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Sample records for absolute isotopic composition

  1. Absolute isotopic composition and atomic weight of neodymium using thermal ionization mass spectrometry.

    PubMed

    Zhao, Motian; Zhou, Tao; Wang, Jun; Lu, Hai; Fang, Xiang; Guo, Chunhua; Li, Qiuli; Li, Chaofeng

    2005-01-01

    Synthetic mixtures prepared gravimetrically from highly enriched isotopes of neodymium in the form of oxides of well-defined purity were used to calibrate a thermal ionization mass spectrometer. A new error analysis was applied to calculate the final uncertainty of the atomic weight value. Measurements on natural neodymium samples yielded an absolute isotopic composition of 27.153(19) atomic percent (at.%) 142Nd, 12.173(18) at.% 143Nd, 23.798(12) at.% 144Nd, 8.293(7) at.% 145Nd, 17.189(17) at.% 146Nd, 5.756(8) at.% 148Nd, and 5.638(9) at.% 150Nd, and the atomic weight of neodymium as 144.2415(13), with uncertainties given on the basis of 95% confidence limits. No isotopic fractionation was found in terrestrial neodymium materials.

  2. Absolute isotopic composition of molybdenum and the solar abundances of the p-process nuclides Mo92,94

    NASA Astrophysics Data System (ADS)

    Wieser, M. E.; de Laeter, J. R.

    2007-05-01

    The isotopic composition of molybdenum has been measured with high precision using a thermal ionization mass spectrometer, the linearity of which has been verified by measuring the isotopically-certified reference material for strontium (NIST 987). The abundance sensitivity of the mass spectrometer in the vicinity of the molybdenum ion beams has been carefully examined to ensure the absence of tailing effects. Particular care was given to ensuring that potential isobaric interferences from zirconium and ruthenium did not affect the measurement of the isotopic composition of molybdenum. Gravimetric mixtures of two isotopically enriched isotopes, Mo92 and Mo98, were analyzed mass spectrometrically to calibrate the mass spectrometer, in order to establish the isotope fractionation of the spectrometer for the molybdenum isotopes. This enabled the “absolute” isotopic composition of molybdenum to be determined. An accurate determination of the isotopic composition is required in order to calculate the atomic weight of molybdenum, which is one of the least accurately known values of all the elements. The absolute isotope abundances (in atom %) of molybdenum measured in this experiment are as follows: Mo92=14.5246±0.0015; Mo94=9.1514±0.0074; Mo95=15.8375±0.0098; Mo96=16.672±0.019; Mo97=9.5991±0.0073; Mo98=24.391±0.018; and Mo100=9.824±0.050, with uncertainties at the 1s level. These values enable an atomic weight Ar(Mo) of 95.9602±0.0023 (1s) to be calculated, which is slightly higher than the current Standard Atomic Weight Ar(Mo) =95.94±0.02 and with a much improved uncertainty interval. These “absolute” isotope abundances also enable the Solar System abundances of molybdenum to be calculated for astrophysical purposes. Of particular interest are the Solar System abundances of the two p-process nuclides—Mo92 and Mo94, which are present in far greater abundance than p-process theory suggests. The Solar System abundances for Mo92 and Mo94 of 0.364±0

  3. Absolute photoneutron cross sections of Sm isotopes

    SciTech Connect

    Gheorghe, I.; Glodariu, T.; Utsunomiya, H.; Filipescu, D.; Nyhus, H.-T.; Renstrom, T.; Tesileanu, O.; Shima, T.; Takahisa, K.; Miyamoto, S.

    2015-02-24

    Photoneutron cross sections for seven samarium isotopes, {sup 144}Sm, {sup 147}Sm, {sup 148}Sm, {sup 149}Sm, {sup 150}Sm, {sup 152}Sm and {sup 154}Sm, have been investigated near neutron emission threshold using quasimonochromatic laser-Compton scattering γ-rays produced at the synchrotron radiation facility NewSUBARU. The results are important for nuclear astrophysics calculations and also for probing γ-ray strength functions in the vicinity of neutron threshold. Here we describe the neutron detection system and we discuss the related data analysis and the necessary method improvements for adapting the current experimental method to the working parameters of the future Gamma Beam System of Extreme Light Infrastructure - Nuclear Physics facility.

  4. Atomic Weights and Isotopic Compositions

    National Institute of Standards and Technology Data Gateway

    SRD 144 Atomic Weights and Isotopic Compositions (Web, free access)   The atomic weights are available for elements 1 through 111, and isotopic compositions or abundances are given when appropriate.

  5. Absolute Isotopic Abundance Ratios and Atomic Weight of a Reference Sample of Nickel

    PubMed Central

    Gramlich, J. W.; Machlan, L. A.; Barnes, I. L.; Paulsen, P. J.

    1989-01-01

    Absolute values have been obtained for the isotopic abundance ratios of a reference sample of nickel (Standard Reference Material 986), using thermal ionization mass spectrometry. Samples of known isotopic composition, prepared from nearly isotopically pure separated nickel isotopes, were used to calibrate the mass spectrometers. The resulting absolute isotopic ratios are: 58Ni/60Ni=2.596061±0.000728, 61Ni/60Ni=0.043469±0.000015,62Ni/60Ni=0.138600±0.000045, and 64Ni/60Ni=0.035295±0.000024, which yield atom percents of 58Ni=68.076886 ±0.005919, 60Ni = 26.223146±0.005144,61Ni=1.139894±0.000433, 62Ni =3.634528±0.001142, and 64Ni =0.925546±0.000599. The atomic weight calculated from this isotopic composition is 58.693353 ±0.000147. The indicated uncertainties are overall limits of error based on two standard deviations of the mean and allowances for the effects of known sources of possible systematic error. PMID:28053421

  6. Chemical composition of French mimosa absolute oil.

    PubMed

    Perriot, Rodolphe; Breme, Katharina; Meierhenrich, Uwe J; Carenini, Elise; Ferrando, Georges; Baldovini, Nicolas

    2010-02-10

    Since decades mimosa (Acacia dealbata) absolute oil has been used in the flavor and perfume industry. Today, it finds an application in over 80 perfumes, and its worldwide industrial production is estimated five tons per year. Here we report on the chemical composition of French mimosa absolute oil. Straight-chain analogues from C6 to C26 with different functional groups (hydrocarbons, esters, aldehydes, diethyl acetals, alcohols, and ketones) were identified in the volatile fraction. Most of them are long-chain molecules: (Z)-heptadec-8-ene, heptadecane, nonadecane, and palmitic acid are the most abundant, and constituents such as 2-phenethyl alcohol, methyl anisate, and ethyl palmitate are present in smaller amounts. The heavier constituents were mainly triterpenoids such as lupenone and lupeol, which were identified as two of the main components. (Z)-Heptadec-8-ene, lupenone, and lupeol were quantified by GC-MS in SIM mode using external standards and represents 6%, 20%, and 7.8% (w/w) of the absolute oil. Moreover, odorant compounds were extracted by SPME and analyzed by GC-sniffing leading to the perception of 57 odorant zones, of which 37 compounds were identified by their odorant description, mass spectrum, retention index, and injection of the reference compound.

  7. Magnesium isotopic composition of achondrites

    NASA Astrophysics Data System (ADS)

    Sedaghatpour, Fatemeh; Teng, Fang-Zhen

    2016-02-01

    Magnesium isotopic compositions of 22 well-characterized differentiated meteorites including 7 types of achondrites and pallasite meteorites were measured to estimate the average Mg isotopic composition of their parent bodies and evaluate Mg isotopic heterogeneity of the solar system. The δ26Mg values are -0.236‰ and -0.190‰ for acapulcoite-lodranite and angrite meteorites, respectively and vary from -0.267‰ to -0.222‰ in the winonaite-IAB-iron silicate group, -0.369‰ to -0.292‰ in aubrites, -0.269‰ to -0.158‰ in HEDs, -0.299‰ to -0.209‰ in ureilites, -0.307‰ to -0.237‰ in mesosiderites, and -0.303‰ to -0.238‰ in pallasites. Magnesium isotopic compositions of most achondrites and pallasite meteorites analyzed here are similar and reveal no significant isotopic fractionation. However, Mg isotopic compositions of D‧Orbigny (angrite) and some HEDs are slightly heavier than chondrites and the other achondrites studied here. The slightly heavier Mg isotopic compositions of angrites and some HEDs most likely resulted from either impact-induced evaporation or higher abundance of clinopyroxene with the Mg isotopic composition slightly heavier than olivine and orthopyroxene. The average Mg isotopic composition of achondrites (δ26Mg = -0.246 ± 0.082‰, 2SD, n = 22) estimated here is indistinguishable from those of the Earth (δ26Mg = -0.25 ± 0.07‰; 2SD, n = 139), chondrites (δ26Mg = -0.28 ± 0.06‰; 2SD, n = 38), and the Moon (δ26Mg = -0.26 ± 0.16‰; 2SD, n = 47) reported from the same laboratory. The chondritic Mg isotopic composition of achondrites, the Moon, and the Earth further reflects homogeneity of Mg isotopes in the solar system and the lack of Mg isotope fractionation during the planetary accretion process and impact events.

  8. Calcium isotopic compositions of chondrites

    NASA Astrophysics Data System (ADS)

    Huang, Shichun; Jacobsen, Stein B.

    2017-03-01

    We report mass-dependent and mass-independent Ca isotopic variations in nine chondrites from three groups: carbonaceous, ordinary and enstatite chondrites. There is about 0.25‰ per amu, i.e., ∼1‰ in 44Ca/40Ca, variation in chondrites: carbonaceous chondrites have the lightest Ca isotopes, enstatite chondrites have modeled bulk Earth like Ca isotopes, and ordinary chondrites are in between. The correlations between mass-dependent Ca isotopic variation and chemical variations in chondrites may reflect variable contributions from different endmembers, including refractory inclusions, in different chondrite groups. In detail, enstatite chondrites and the Earth share similar isotopic characteristics, but are very different in chemical compositions. At the ±1 and ±2 ε-unit levels, respectively, there is no measurable 40Ca or 43Ca anomaly in bulk chondrites. Carbonaceous chondrites show several ε-units of 48Ca excess. That is, Ca exhibits both mass-dependent and mass-independent isotopic variations in chondrites, similar to O isotopes. The 48Ca anomaly in bulk chondrites is positively correlated with 50Ti anomaly, but does not form simple correlation with 54Cr anomaly, implying multiple supernova sources for these neutron-rich isotopes in the Solar System. Finally, all meteorites with negative Δ17O have either 48Ca deficits (differentiated meteorites) or 48Ca excess (carbonaceous chondrites), implying that the Sun with a very negative Δ17O is probably also characterized by 48Ca anomaly compared to the Earth. CAIs cannot be taken as representative of the initial isotopic compositions of refractory elements like Ca for the Earth-Moon system.

  9. Oxygen Isotopic Compositions of Fulgurites

    NASA Astrophysics Data System (ADS)

    Robert, F.; Javoy, M.

    1992-07-01

    Two occurrences of vitreous rocks (fulgurites) that have resulted from the fusion of Etnean lavas, have been ascribed to the result of lightning striking the basalts and melting fresh volcanic rocks [1]. Rapidly quenched melts appear as tubular cavities that preserve the path of the discharge. Glass droplets (D <= 500 micrometers) are always dispersed around the fused lava tube and show several petrographic similarities with chondrules found in ordinary chondrites (presence of melilite, radiating skeletal fassaite, etc). In this process, high temperatures (T>1800 K) have probably been reached during timescales <=10 sec. Because it has been suggested that lightning discharges may have played an important role in the formation of chondrules [2], we have analyzed the oxygen isotope compositions of these fulgurites (our experimental protocol is described elsewhere [3]). The glass (free from any contamination from the unmelted basalt) is 1.5o/oo depleted in ^18O relative to its measured initial isotopic composition (delta^18O = +5.6o/oo); most of the data define a mass-dependent fractionation relationship (i.e. delta^17O = 0.52 x delta^18O). Therefore the data clearly do not reproduce the oxygen isotope anomaly defined for meteorites, which has a slope of 1 in the diagram delta^17O versus delta^18O (i.e. delta^17O = 1.0 x delta^18O). Nevertheless, it should be noted that some glass samples scatter around this canonical value of 0.52 with minor departures from a purely mass-dependent fractionation. If these results are confirmed by additional determinations (now in progress) on the separated glassy droplets, the following conclusions can be proposed: 1) lightning discharges do not yield oxygen isotope anomalies similar to those measured in chondrules and 2) an isotope exchange between hot chondrules and their parent nebular gas--presumably "anomalous" in its oxygen isotopes-- seems difficult to achieve within the duration of the rapid cooling of the melt. This last point

  10. Grosnaja ABCs: Magnesium isotope compositions

    NASA Technical Reports Server (NTRS)

    Goswami, J. N.; Srinivasan, G.; Ulyanov, A. A.

    1993-01-01

    Three CAI's from the Grosnaja CV3 chondrite were analyzed for their magnesium isotopic compositions by the ion microprobe. The selected CAI's represent three distinct types: GR4(compact Type A), GR7(Type B) and GR2(Type C). Petrographic studies indicate that all three Grosnaja inclusions were subjected to secondary alterations. The Type A CAI GR4 is primarily composed of melilite with spinel and pyroxene occurring as minor phases. The rim of the inclusion does not exhibit distinct layered structure and secondary alteration products (garnet, Fe-rich olivine and Na-rich plagioclase) are present in some localized areas near the rim region. The average major element compositions of different mineral phases in GR4 are given. Preliminary REE data suggest a depletion of HREE relative to LREE by about a factor of 3 without any clear indication of interelement fractionation. The CAI GR7 has textural and minerological characteristics similar to Type B inclusions. The REE data show a pattern that is similar to Group 6 with enrichment in Eu and Yb. In addition, a depletion of HREE compared to LREE is also evident in this object. Melilite composition shows a broad range of akermanite content (Ak(sub 15-55)). Detailed petrographic study is in progress. GR2 is a anorthite-rich Type C inclusion with large plagioclase laths intergrown with Ti-rich pyroxene. The average plagioclase composition is close to pure anorthite (An99).

  11. Metal Stable Isotope Tagging: Renaissance of Radioimmunoassay for Multiplex and Absolute Quantification of Biomolecules.

    PubMed

    Liu, Rui; Zhang, Shixi; Wei, Chao; Xing, Zhi; Zhang, Sichun; Zhang, Xinrong

    2016-05-17

    The unambiguous quantification of biomolecules is of great significance in fundamental biological research as well as practical clinical diagnosis. Due to the lack of a detectable moiety, the direct and highly sensitive quantification of biomolecules is often a "mission impossible". Consequently, tagging strategies to introduce detectable moieties for labeling target biomolecules were invented, which had a long and significant impact on studies of biomolecules in the past decades. For instance, immunoassays have been developed with radioisotope tagging by Yalow and Berson in the late 1950s. The later languishment of this technology can be almost exclusively ascribed to the use of radioactive isotopes, which led to the development of nonradioactive tagging strategy-based assays such as enzyme-linked immunosorbent assay, fluorescent immunoassay, and chemiluminescent and electrochemiluminescent immunoassay. Despite great success, these strategies suffered from drawbacks such as limited spectral window capacity for multiplex detection and inability to provide absolute quantification of biomolecules. After recalling the sequences of tagging strategies, an apparent question is why not use stable isotopes from the start? A reasonable explanation is the lack of reliable means for accurate and precise quantification of stable isotopes at that time. The situation has changed greatly at present, since several atomic mass spectrometric measures for metal stable isotopes have been developed. Among the newly developed techniques, inductively coupled plasma mass spectrometry is an ideal technique to determine metal stable isotope-tagged biomolecules, for its high sensitivity, wide dynamic linear range, and more importantly multiplex and absolute quantification ability. Since the first published report by our group, metal stable isotope tagging has become a revolutionary technique and gained great success in biomolecule quantification. An exciting research highlight in this area

  12. Isotopic Compositions of the Elements, 2001

    NASA Astrophysics Data System (ADS)

    Böhlke, J. K.; de Laeter, J. R.; De Bièvre, P.; Hidaka, H.; Peiser, H. S.; Rosman, K. J. R.; Taylor, P. D. P.

    2005-03-01

    The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the "best measurement" of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E) and its uncertainty U[Ar(E)] recommended by CAWIA in 2001.

  13. Isotopic compositions of the elements, 2001

    USGS Publications Warehouse

    Böhlke, J.K.; De Laeter, J. R.; De Bievre, P.; Hidaka, H.; Peiser, H.S.; Rosman, K.J.R.; Taylor, P.D.P.

    2005-01-01

    The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the "best measurement" of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element A r(E) and its uncertainty U[Ar(E)] recommended by CAWIA in 2001. ?? 2005 American Institute of Physics.

  14. Unusual mercury isotopic compositions in aqueous environment

    NASA Astrophysics Data System (ADS)

    Chen, J.; Hintelmann, H.; Zheng, W.; Feng, X.; Cai, H.; Wang, Z.; Yuan, S.

    2014-12-01

    Preliminary studies have demonstrated both mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) of Hg isotopes in natural samples. Laboratory experiments showed that photochemical reduction of inorganic mercury (iHg) and methylmercury (MMHg) and liquid-vapour evaporation could produce MIF of odd Hg isotopes. This was thought to cause the MIF actually observed in aquatic organisms. Although isotopic measurements of Hg in aqueous environment would give direct evidence, little data was reported for surface water samples. Recent work reported, unexpectedly, positive MIF of odd Hg isotopes in both precipitation and ambient air, in contrast with the prediction of laboratory experiments and measurements of Hg accumulated in lichens . Intriguingly, MIF of even-mass Hg isotope (200Hg) was also recently determined in the atmosphere. In contrast with the now mainstream observation of odd Hg isotope anomaly that has several theoretical explanations, the hitherto mysterious even Hg isotope anomalies were neither reported in laboratory experiments, nor predicted by isotope fractionation mechanisms, highlighting the importance of further study on Hg isotopes in variable systems. Our measurements of lichens and lake water samples from different countries show for the first time significant Δ200Hg in surface terrestrial reservoirs, realizing a direct connection of even Hg isotope anomaly in the terrestrial reservoirs to the atmospheric deposition, and fulfilling the gap of Δ200Hg between the atmosphere and the terrestrial receptors. The specific odd Hg isotope compositions determined in lake waters also support the atmosphere contribution, and may be directly linked to the high Δ199Hg values largely determined and manifested on the top of aqueous food web. Our data show that the watershed Hg input is another contributing source, rather than the in-lake processes, to explain the lacustrine Hg isotope anomalies. Interestingly, lake sediments are isotopically

  15. Anomalous gain in an isotopically mixed CO2 laser and application to absolute wavelength calibration

    NASA Technical Reports Server (NTRS)

    Hewagama, Tilak; Oppenheim, Uri P.; Mumma, Michael J.

    1991-01-01

    Measurements are reported on a grating-tuned CO2 laser, containing an isotropic mixture of O-16C-12O-16, O-16C-12O-18, and O-18C-12O-18. The P6 and R14 lines of O-16C-12O-16 were found to have anomalously high intensities. These anomalies are produced by the near coincidence of the transition frequencies in two distinct isotopes, permitting them to act as a single indistinguishable population. These two lines can be used to identify the rotational quantum numbers in the P and R branch spectra, thereby permitting absolute wavelength calibration to be achieved.

  16. Nucleosynthesis and the Isotopic Composition of Stardust

    NASA Technical Reports Server (NTRS)

    Tielens, Alexander G. M.

    1997-01-01

    Various components have been isolated from carbonaceous meteorites with an isotopically anomalous elemental composition. Several of these are generally thought to represent stardust containing a nucleosynthetic record of their birthsites. This paper discusses the expected isotopic composition of stardust based upon astronomical observations and theoretical studies of their birthsites: red giants and supergiants, planetary nebulae, C-rich Wolf-Rayet stars, novae and supernovae. Analyzing the stardust budget, it is concluded that about 15% of the elements will be locked up in stardust components in the interstellar medium. This stardust will be isotopically heterogenous on an individual grain basis by factors ranging from 2 to several orders of magnitude. Since comets may have preserved a relatively unprocessed record of the stardust entering the solar nebula, isotopic studies of returned comet samples may provide valuable information on the nucleosynthetic processes taking place in the interiors of stars and the elemental evolution of the Milky Way.

  17. Nickel isotopic composition of the mantle

    NASA Astrophysics Data System (ADS)

    Gall, Louise; Williams, Helen M.; Halliday, Alex N.; Kerr, Andrew C.

    2017-02-01

    This paper presents a detailed high-precision study of Ni isotope variations in mantle peridotites and their minerals, komatiites as well as chondritic and iron meteorites. Ultramafic rocks display a relatively large range in δ60 Ni (permil deviation in 60 Ni /58 Ni relative to the NIST SRM 986 Ni isotope standard) for this environment, from 0.15 ± 0.07‰ to 0.36 ± 0.08‰, with olivine-rich rocks such as dunite and olivine cumulates showing lighter isotope compositions than komatiite, lherzolite and pyroxenite samples. The data for the mineral separates shed light on the origin of these variations. Olivine and orthopyroxene display light δ60 Ni whereas clinopyroxene and garnet are isotopically heavy. This indicates that peridotite whole-rock δ60 Ni may be controlled by variations in modal mineralogy, with the prediction that mantle melts will display variable δ60 Ni values due to variations in residual mantle and cumulate mineralogy. Based on fertile peridotite xenoliths and Phanerozoic komatiite samples it is concluded that the upper mantle has a relatively homogeneous Ni isotope composition, with the best estimate of δ60Nimantle being 0.23 ± 0.06‰ (2 s.d.). Given that >99% of the Ni in the silicate Earth is located in the mantle, this also defines the Ni isotope composition of the Bulk Silicate Earth (BSE). This value is nearly identical to the results obtained for a suite of chondrites and iron meteorites (mean δ60 Ni 0.26 ± 0.12‰ and 0.29 ± 0.10‰, respectively) showing that the BSE is chondritic with respect to its Ni isotope composition, with little to no Ni mass-dependent isotope fractionation resulting from core formation.

  18. Absolute peptide quantification by lutetium labeling and nanoHPLC-ICPMS with isotope dilution analysis.

    PubMed

    Rappel, Christina; Schaumlöffel, Dirk

    2009-01-01

    The need of analytical methods for absolute quantitative protein analysis spurred research on new developments in recent years. In this work, a novel approach was developed for accurate absolute peptide quantification based on metal labeling with lutetium diethylenetriamine pentaacetic acid (Lu-DTPA) and nanoflow high-performance liquid chromatography-inductively coupled plasma isotope dilution mass spectrometry (nanoHPLC-ICP-IDMS). In a two-step procedure peptides were derivatized at amino groups with diethylenetriamine pentaacetic anhydride (DTPAA) followed by chelation of lutetium. Electrospray ionization mass spectrometry (ESI MS) of the reaction product demonstrated highly specific peptide labeling. Under optimized nanoHPLC conditions the labeled peptides were baseline-separated, and the excess labeling reagent did not interfere. A 176Lu-labeled spike was continuously added to the column effluent for quantification by ICP-IDMS. The recovery of a Lu-DTPA-labeled standard peptide was close to 100% indicating high labeling efficiency and accurate absolute quantification. The precision of the entire method was 4.9%. The detection limit for Lu-DTPA-tagged peptides was 179 amol demonstrating that lutetium-specific peptide quantification was by 4 orders of magnitude more sensitive than detection by natural sulfur atoms present in cysteine or methionine residues. Furthermore, the application to peptides in insulin tryptic digest allowed the identification of interfering reagents decreasing the labeling efficiency. An additional advantage of this novel approach is the analysis of peptides, which do not naturally feature ICPMS-detectable elements.

  19. Recombinant isotope labeled and selenium quantified proteins for absolute protein quantification.

    PubMed

    Zinn, Nico; Winter, Dominic; Lehmann, Wolf D

    2010-03-15

    A novel, widely applicable method for the production of absolutely quantified proteins is described, which can be used as internal standards for quantitative proteomic studies based on mass spectrometry. These standards are recombinant proteins containing an isotope label and selenomethionine. For recombinant protein expression, assembly of expression vectors fitted to cell-free protein synthesis was conducted using the gateway technology which offers fast access to a variety of genes via open reading frame libraries and an easy shuttling of genes between vectors. The proteins are generated by cell-free expression in a medium in which methionine is exchanged against selenomethionine and at least one amino acid is exchanged by a highly stable isotope labeled analogue. After protein synthesis and purification, selenium is used for absolute quantification by element mass spectrometry, while the heavy amino acids in the protein serve as reference in subsequent analyses by LC-ESI-MS or MALDI-MS. Accordingly, these standards are denominated RISQ (for recombinant isotope labeled and selenium quantified) proteins. In this study, a protein was generated containing Lys+6 ([(13)C(6)]-lysine) and Arg+10 ([(13)C(6),(15)N(4)]-arginine) so that each standard tryptic peptide contains a labeled amino acid. Apolipoprotein A1 was synthesized as RISQ protein, and its use as internal standard led to quantification of a reference material within the specified value. Owing to their cell-free expression, RISQ proteins do not contain posttranslational modifications. Thus, correct quantitative data by ESI- or MALDI-MS are restricted to quantifications based on peptides derived from unmodified regions of the analyte protein. Therefore, besides serving as internal standards, RISQ proteins stand out as new tools for quantitative analysis of covalent protein modifications.

  20. Calcium isotopic composition of mantle peridotites

    NASA Astrophysics Data System (ADS)

    Huang, F.; Kang, J.; Zhang, Z.

    2015-12-01

    Ca isotopes are useful to decipher mantle evolution and the genetic relationship between the Earth and chondrites. It has been observed that Ca isotopes can be fractionated at high temperature [1-2]. However, Ca isotopic composition of the mantle peridotites and fractionation mechanism are still poorly constrained. Here, we report Ca isotope composition of 12 co-existing pyroxene pairs in 10 lherzolites, 1 harzburgite, and 1 wehrlite xenoliths collected from Hainan Island (South Eastern China). Ca isotope data were measured on a Triton-TIMS using the double spike method at the Guangzhou Institute of Geochemistry, CAS. The long-term external error is 0.12‰ (2SD) based on repeated analyses of NIST SRM 915a and geostandards. δ44Ca of clinopyroxenes except that from the wehrlite ranges from 0.85‰ to 1.14‰, while opx yields a wide range from 0.98‰ up to 2.16‰. Co-existing pyroxene pairs show large ∆44Caopx-cpx (defined as δ44Caopx-δ44Cacpx) ranging from 0 to 1.23‰, reflecting equilibrium fractionation controlled by variable Ca contents in the opx. Notably, clinopyroxene of wehrlite shows extremely high δ44Ca (3.22‰). δ44Ca of the bulk lherzolites and harzburgites range from 0.86‰ to 1.14‰. This can be explained by extracting melts with slightly light Ca isotopic compositions. Finally, the high δ44Ca of the wehrlite (3.22‰) may reflect metasomatism by melt which has preferentially lost light Ca isotopes due to chemical diffusion during upwelling through the melt channel. [1] Amini et al (2009) GGR 33; [2] Huang et al (2010) EPSL 292.

  1. The Chlorine Isotope Composition of Martian Meteorites

    NASA Astrophysics Data System (ADS)

    Sharp, Z. D.; Shearer, C. K.; Agee, C.; Burger, P. V.; McKeegan, K. D.

    2014-11-01

    The Cl isotope composition of martian meteorites range from -3.8 to +8.6 per mil. Ol-phyric shergottites are lightest; crustally contaminated samples are heaviest, basaltic shergottites are in-between. The system is explained as two component mixing.

  2. Isotopic composition of Silurian seawater

    SciTech Connect

    Knauth, L.P.; Kealy, S.; Larimer, S.

    1985-01-01

    Direct isotopic analyses of 21 samples of the Silurian hydrosphere preserved as fluid inclusions in Silurian halite deposits in the Michigan Basin Salina Group yield delta/sup 18/O, deltaD ranging from 0.2 to +5.9 and -26 to -73, respectively. delta/sup 18/O has the same range as observed for modern halite facies evaporite waters and is a few per thousand higher than 100 analyses of fluid inclusions in Permian halite. deltaD is about 20 to 30 per thousand lower than modern and Permian examples. The trajectory of evaporating seawater on a deltaD-delta/sup 18/O diagram initially has a positive slope of 3-6, but hooks strongly downward to negative values, the shape of the hook depending upon humidity. Halite begins to precipitate at delta values similar to those observed for the most /sup 18/O rich fluid inclusions. Subsequent evaporation yields progressively more negative delta values as observed for the fluid inclusions. The fluid inclusion data can be readily explained in terms of evaporating seawater and are consistent with the degree of evaporation deduced from measured bromide profiles. These data are strongly inconsistent with arguments that Silurian seawater was 5.5 per thousand depleted in /sup 18/O. delta/sup 18/O for evaporite waters is systematically related to that of seawater, and does not show a -5.5 per thousand shift in the Silurian, even allowing for variables which affect the isotope evaporation trajectory. The lower deltaD may indicate a component of gypsum dehydration waters or may suggest a D-depleted Silurian hydrosphere.

  3. Isotopic composition of formaldehyde in urban air.

    PubMed

    Rice, Andrew L; Quay, Paul

    2009-12-01

    The isotopic composition of atmospheric formaldehyde was measured in air samples collected in urban Seattle, Washington. A recently developed gas chromatography-isotope ratio mass spectrometry analytical technique was used to extract formaldehyde directly from whole air, separate it from other volatile organic compounds, and measure its (13)C/(12)C and D/H ratio. Measurements of formaldehyde concentration were also made concomitant with isotope ratio. Results of the analysis of nine discrete air samples for delta(13)C-HCHO have a relatively small range in isotopic composition (-31 to -25 per thousand versus VPDB [+/-1.3 per thousand]) over a considerable concentration range (0.8-4.4 ppb [+/-15%]). In contrast, analyses of 17 air samples for deltaD-HCHO show a large range (-296 to +210 per thousand versus VSMOW [+/-50 per thousand]) over the concentrations measured (0.5-2.9 ppb). Observations of deltaD are weakly anticorrelated with concentration. Isotopic data are interpreted using both source- and sink-based approaches. Results of delta(13)C-HCHO are similar to those observed previously for a number of nonmethane hydrocarbons in urban environments and variability can be reconciled with a simple sink-based model. The large variability observed in deltaD-HCHO favors a source-based interpretation with HCHO depleted in deuterium from primary sources of HCHO (i.e., combustion) and HCHO enriched in deuterium from secondary photochemical sources (i.e., hydrocarbon oxidation).

  4. Sulfur-based absolute quantification of proteins using isotope dilution inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Lee, Hyun-Seok; Heun Kim, Sook; Jeong, Ji-Seon; Lee, Yong-Moon; Yim, Yong-Hyeon

    2015-10-01

    An element-based reductive approach provides an effective means of realizing International System of Units (SI) traceability for high-purity biological standards. Here, we develop an absolute protein quantification method using double isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP-MS) combined with microwave-assisted acid digestion for the first time. We validated the method and applied it to certify the candidate protein certified reference material (CRM) of human growth hormone (hGH). The concentration of hGH was determined by analysing the total amount of sulfur in hGH. Next, the size-exclusion chromatography method was used with ICP-MS to characterize and quantify sulfur-containing impurities. By subtracting the contribution of sulfur-containing impurities from the total sulfur content in the hGH CRM, we obtained a SI-traceable certification value. The quantification result obtained with the present method based on sulfur analysis was in excellent agreement with the result determined via a well-established protein quantification method based on amino acid analysis using conventional acid hydrolysis combined with an ID liquid chromatography-tandem mass spectrometry. The element-based protein quantification method developed here can be generally used for SI-traceable absolute quantification of proteins, especially pure-protein standards.

  5. Establishing ion ratio thresholds based on absolute peak area for absolute protein quantification using protein cleavage isotope dilution mass spectrometry.

    PubMed

    Loziuk, Philip L; Sederoff, Ronald R; Chiang, Vincent L; Muddiman, David C

    2014-11-07

    Quantitative mass spectrometry has become central to the field of proteomics and metabolomics. Selected reaction monitoring is a widely used method for the absolute quantification of proteins and metabolites. This method renders high specificity using several product ions measured simultaneously. With growing interest in quantification of molecular species in complex biological samples, confident identification and quantitation has been of particular concern. A method to confirm purity or contamination of product ion spectra has become necessary for achieving accurate and precise quantification. Ion abundance ratio assessments were introduced to alleviate some of these issues. Ion abundance ratios are based on the consistent relative abundance (RA) of specific product ions with respect to the total abundance of all product ions. To date, no standardized method of implementing ion abundance ratios has been established. Thresholds by which product ion contamination is confirmed vary widely and are often arbitrary. This study sought to establish criteria by which the relative abundance of product ions can be evaluated in an absolute quantification experiment. These findings suggest that evaluation of the absolute ion abundance for any given transition is necessary in order to effectively implement RA thresholds. Overall, the variation of the RA value was observed to be relatively constant beyond an absolute threshold ion abundance. Finally, these RA values were observed to fluctuate significantly over a 3 year period, suggesting that these values should be assessed as close as possible to the time at which data is collected for quantification.

  6. Mercury isotope compositions across North American forests

    NASA Astrophysics Data System (ADS)

    Zheng, Wang; Obrist, Daniel; Weis, Dominique; Bergquist, Bridget A.

    2016-10-01

    Forest biomass and soils represent some of the largest reservoirs of actively cycling mercury (Hg) on Earth, but many uncertainties exist regarding the source and fate of Hg in forest ecosystems. We systematically characterized stable isotope compositions of Hg in foliage, litter, and mineral soil horizons across 10 forest sites in the contiguous United States. The mass-independent isotope signatures in all forest depth profiles are more consistent with those of atmospheric Hg(0) than those of atmospheric Hg(II), indicating that atmospheric Hg(0) is the larger source of Hg to forest ecosystems. Within litter horizons, we observed significant enrichment in Hg concentration and heavier isotopes along the depth, which we hypothesize to result from additional deposition of atmospheric Hg(0) during litter decomposition. Furthermore, Hg isotope signatures in mineral soils closely resemble those of the overlying litter horizons suggesting incorporation of Hg from litter as a key source of soil Hg. The spatial distribution of Hg isotope compositions in mineral soils across all sites is modeled by isotopic mixing assuming atmospheric Hg(II), atmospheric Hg(0), and geogenic Hg as major sources. This model shows that northern sites with higher precipitation tend to have higher atmospheric Hg(0) deposition than other sites, whereas drier sites in the western U.S. tend to have higher atmospheric Hg(II) deposition than the rest. We attribute these differences primarily to the higher litterfall Hg input at northern wetter sites due to increased plant productivity by precipitation. These results allow for a better understanding of Hg cycling across the atmosphere-forest-soil interface.

  7. Some triple-filament lead isotope ratio measurements and an absolute growth curve for single-stage leads

    USGS Publications Warehouse

    Stacey, J.S.; Delevaux, M.E.; Ulrych, T.J.

    1969-01-01

    Triple-filament analyses of three standard lead samples are used to calibrate a mass spectrometer in an absolute sense. The bias we measure is 0.0155 percent per mass unit, and the precision (for 95% confidence limits) is ??0.13% or less for all ratios relative to 204Pb. Although its precision is not quite so good as that of the lead-tetramethyl method in the analysis of large samples, the triple-filament method is less complex and is an attractive alternative for smaller sample sizes down to 500 ??g. Triple-filament data are presented for six possibly single-stage lead ores and one feldspar. These new data for ores are combined with corrected tetramethyl data for stratiform lead deposits to compute absolute parameters for a universal single-stage lead isotope growth curve. Absolute isotopic ratios for primeval lead have been determined by Oversby and because all the previous data for both meteorites and lead ores were similarly fractionated, the absolute value of 238U 204Pb = 9.09 ?? 0.06 for stratiform leads is little different from the value 8.99 ?? 0.05 originally computed by Ostic, Russell and Stanton. Absolute values for lead isotope ratios for all interlaboratory standard samples presently available from the literature are tabulated. ?? 1969.

  8. ISOTOPIC COMPOSITIONS OF URANIUM REFERENCE MATERIALS

    SciTech Connect

    Jacobsen, B; Borg, L; Williams, R; Brennecka, G; Hutcheon, I

    2009-09-03

    Uranium isotopic compositions of a variety of U standard materials were measured at Lawrence Livermore National Laboratory and are reported here. Both thermal ionization mass spectrometry (TIMS) and multi-collector inductively couple plasma mass spectrometry (MC-ICPMS) were used to determine ratios of the naturally occurring isotopes of U. Establishing an internally coherent set of isotopic values for a range of U standards is essential for inter-laboratory comparison of small differences in {sup 238}U/{sup 235}U, as well as the minor isotopes of U. Differences of {approx} 1.3{per_thousand} are now being observed in {sup 238}U/{sup 235}U in natural samples, and may play an important role in understanding U geochemistry where tracing the origin of U is aided by U isotopic compositions. The {sup 238}U/{sup 235}U ratios were measured with a TRITON TIMS using a mixed {sup 233}U-{sup 236}U isotopic tracer to correct for instrument fractionation. this tracer was extremely pure and resulted in only very minor corrections on the measured {sup 238}U/{sup 235}U ratios of {approx} 0.03. The values obtained for {sup 238}U/{sup 235}U are: IRMM184 = 137.698 {+-} 0.020 (n = 15), SRM950a = 137.870 {+-} 0.018 (n = 8), and CRM112a = 137.866 {+-} 0.030 (n = 16). Uncertainties represent 2 s.d. of the population. The measured value for IRMM184 is in near-perfect agreement with the certified value of 137.697 {+-} 0.042. However, the U isotopic compositions of SRM950a and CRM112a are not certified. Minor isotopes of U were determined with a Nu Plasma HR MC-ICPMS and mass bias was corrected by sample/standard bracketing to IRMM184, using its certified {sup 238}U/{sup 235}U ratio. Thus, the isotopic compositions determined using both instruments are compatible. The values obtained for {sup 234}U/{sup 235}U are: SRM950a = (7.437 {+-} 0.043) x 10{sup -3} (n = 18), and CRM112a = (7.281 {+-} 0.050) x 10{sup -3} (n = 16), both of which are in good agreement with published values. The value for

  9. Isotopic Composition of Oxygen in Lunar Zircons

    NASA Technical Reports Server (NTRS)

    Nemchin, A. A.; Whitehouse, M. J.; Pidgeon, R. T.; Meyer, C.

    2005-01-01

    The recent discovery of heavy oxygen in zircons from the Jack Hills conglomerates Wilde et al. and Mojzsis et al. was interpreted as an indication of presence of liquid water on the surface of Early Earth. The distribution of ages of Jack Hills zircons and lunar zircons appears to be very similar and therefore analysis of oxygen in the lunar grains may provide a reference frame for further study of the early history of the Earth as well as give additional information regarding processes that operated on the Moon. In the present study we have analysed the oxygen isotopic composition of zircon grains from three lunar samples using the Swedish Museum of Natural History CAMECA 1270 ion microprobe. The samples were selected as likely tests for variations in lunar oxygen isotopic composition. Additional information is included in the original extended abstract.

  10. Sulfur Isotope Composition of Putative Primary Troilite in Chondrules

    NASA Technical Reports Server (NTRS)

    Tachibana, Shogo; Huss, Gary R.

    2002-01-01

    Sulfur isotope compositions of putative primary troilites in chondrules from Bishunpur were measured by ion probe. These primary troilites have the same S isotope compositions as matrix troilites and thus appear to be isotopically unfractionated. Additional information is contained in the original extended abstract.

  11. Advances in the Metrology of Absolute Value Assignments to Isotopic Reference Materials: Consequences from the Avogadro Project

    NASA Astrophysics Data System (ADS)

    Vocke, Robert; Rabb, Savelas

    2015-04-01

    All isotope amount ratios (hereafter referred to as isotope ratios) produced and measured on any mass spectrometer are biased. This unfortunate situation results mainly from the physical processes in the source area where ions are produced. Because the ionized atoms in poly-isotopic elements have different masses, such processes are typically mass dependent and lead to what is commonly referred to as mass fractionation (for thermal ionization and electron impact sources) and mass bias (for inductively coupled plasma sources.) This biasing process produces a measured isotope ratio that is either larger or smaller than the "true" ratio in the sample. This has led to the development of numerous fractionation "laws" that seek to correct for these effects, many of which are not based on the physical processes giving rise to the biases. The search for tighter and reproducible precisions has led to two isotope ratio measurement systems that exist side-by-side. One still seeks to measure "absolute" isotope ratios while the other utilizes an artifact based measurement system called a delta-scale. The common element between these two measurement systems is the utilization of isotope reference materials (iRMs). These iRMs are used to validate a fractionation "law" in the former case and function as a scale anchor in the latter. Many value assignments of iRMs are based on "best measurements" by the original groups producing the reference material, a not entirely satisfactory approach. Other iRMs, with absolute isotope ratio values, have been produced by calibrated measurements following the Atomic Weight approach (AW) pioneered by NBS nearly 50 years ago. Unfortunately, the AW is not capable of calibrating the new generation of iRMs to sufficient precision. So how do we get iRMs with isotope ratios of sufficient precision and without bias? Such a focus is not to denigrate the extremely precise delta-scale measurements presently being made on non-traditional and tradition

  12. The Oxygen Isotopic Composition of the Sun

    NASA Astrophysics Data System (ADS)

    McKeegan, K. D.; Kallio, A.; Heber, V. S.; Jarzebinski, G.; Mao, P.; Coath, C.; Kunihiro, T.; Wiens, R. C.; Judith, A.; Burnett, D. S.

    2010-12-01

    An accurate and precise determination of the oxygen isotopic composition of the Sun is the highest priority scientific goal of the Genesis Mission [1] as such data would provide a baseline from which one could interpret the oxygen isotopic anomalies found at all spatial scales in inner solar system materials. We have measured oxygen isotope compositions of implanted solar wind in 40 spots along a radial traverse of the Genesis SiC target sample 60001 by depth profiling with the UCLA MegaSIMS [2]. Mass-dependent fractionation induced by the solar wind concentrator [3] ion optics was corrected by comparison of the concentrator 22Ne/20Ne with that measured in a bulk solar wind target (diamond-like carbon on Si, [4]). The solar wind captured at L1 has an isotopic composition of (δ18O, δ17O) ≈ (-99, -79)‰, a value which is far removed from the terrestrial mass fractionation line. Profiles from the central portion of the target, where solar concentrations are highest and background corrections minimal, yield a mean Δ17O = -28.3 ± 1.8 ‰ indicating that the Earth and other planetary materials from the inner solar system are highly depleted in 16O relative to the solar wind. A mass-dependent fractionation of ~ -20%/amu in the acceleration of solar wind is required if we hypothesize that the photospheric oxygen isotope value, which represents the bulk starting composition of the solar system, is on the 16O-mixing line characteristic of refractory phase in primitive meteorites [5]. With this assumption, our preferred value for the bulk solar oxygen isotope composition is δ18O ≈ δ17O ≈ -57‰. A mechanism is required to fractionate oxygen isotopes in a non-mass-dependent manner to deplete 16O by ~6 to 7% in the rocky materials of the solar nebula. As oxygen is the third most abundant element in the solar system, and the most abundant in the terrestrial planets, this mechanism must operate on a large scale. Isotope-selective photochemistry, for example as in

  13. THE NITROGEN ISOTOPIC COMPOSITION OF METEORITIC HCN

    SciTech Connect

    Pizzarello, Sandra

    2014-12-01

    HCN is ubiquitous in extraterrestrial environments and is central to current theories on the origin of early solar system organic compounds such as amino acids. These compounds, observed in carbonaceous meteorites, were likely important in the origin and/or evolution of early life. As part of our attempts to understand the origin(s) of meteoritic CN{sup –}, we have analyzed the {sup 15}N/{sup 14}N isotopic composition of HCN gas released from water extracts of the Murchison meteorite and found its value to be near those of the terrestrial atmosphere. The findings, when evaluated viz-a-viz molecular abundances and isotopic data of meteoritic organic compounds, suggest that HCN formation could have occurred during the protracted water alteration processes known to have affected the mineralogy of many asteroidal bodies during their solar residence. This was an active synthetic stage, which likely involved simple gasses, organic molecules, their presolar precursors, as well as mineral catalysts and would have lead to the formation of molecules of differing isotopic composition, including some with solar values.

  14. OXYGEN ISOTOPIC COMPOSITIONS OF SOLAR CORUNDUM GRAINS

    SciTech Connect

    Makide, Kentaro; Nagashima, Kazuhide; Huss, Gary R.; Krot, Alexander N.

    2009-11-20

    Oxygen is one of the major rock-forming elements in the solar system and the third most abundant element of the Sun. Oxygen isotopic composition of the Sun, however, is not known due to a poor resolution of astronomical spectroscopic measurements. Several DELTA{sup 17}O values have been proposed for the composition of the Sun based on (1) the oxygen isotopic measurements of the solar wind implanted into metallic particles in lunar soil (< -20 per mille by Hashizume and Chaussidon and approx +26 per mille by Ireland et al.), (2) the solar wind returned by the Genesis spacecraft (-27 per mille +- 6 per mille by McKeegan et al.), and (3) the mineralogically pristine calcium-aluminum-rich inclusions (CAIs) (-23.3 per mille +- 1.9 per mille by Makide et al. and -35 per mille by Gounelle et al.). CAIs are the oldest solar system solids, and are believed to have formed by evaporation, condensation, and melting processes in hot nebular region(s) when the Sun was infalling (Class 0) or evolved (Class 1) protostar. Corundum (Al{sub 2}O{sub 3}) is thermodynamically the first condensate from a cooling gas of solar composition. Corundum-bearing CAIs, however, are exceptionally rare, suggesting either continuous reaction of the corundum condensates with a cooling nebular gas and their replacement by hibonite (CaAl{sub 12}O{sub 19}) or their destruction by melting together with less refractory condensates during formation of igneous CAIs. In contrast to the corundum-bearing CAIs, isolated micrometer-sized corundum grains are common in the acid-resistant residues from unmetamorphosed chondrites. These grains could have avoided multistage reprocessing during CAI formation and, therefore, can potentially provide constraints on the initial oxygen isotopic composition of the solar nebula, and, hence, of the Sun. Here we report oxygen isotopic compositions of approx60 micrometer-sized corundum grains in the acid-resistant residues from unequilibrated ordinary chondrites (Semarkona (LL3

  15. Molybdenum Isotopic Composition of Iron Meteorites, Chondrites and Refractory Inclusions

    NASA Technical Reports Server (NTRS)

    Becker, H.; Walker, R. J.

    2003-01-01

    Recent Mo isotopic studies of meteorites reported evidence for differences in isotopic compositions for whole rocks of some primitive and differentiated meteorites relative to terrestrial materials. Enrichments of r- and p-process isotopes of up to 3-4 units (e unit = parts in 10(exp 4) over s-process dominated isotopes are the most prominent features. Certain types of presolar grains show large enrichments in s-process isotopes, however, it was concluded on grounds of mass balance that incomplete digestion of such grains cannot explain the enrichments of r- and p-process isotopes in whole rocks of primitive chondrites. If the reported variability in r- and p-process isotope enrichments reflects the true isotopic characteristics of the whole rocks, the implications are quite profound. It would suggest the presence of large scale Mo isotopic heterogeneity within the solar accretion disk with likely collateral effects for other elements. However, such effects were not found for Ru isotopes, nor for Zr isotopes. Another recent Mo isotopic study by multi collector ICP-MS could not confirm the reported deviations in Allende, Murchison or iron meteorites. Here, we present new results for the Mo isotopic composition of iron meteorites, chondrites and CAIs obtained by negative thermal ionization mass spectrometry (NTIMS). We discuss analytical aspects and the homogeneity of Mo isotopic compositions in solar system materials.

  16. Isotopic composition of Riyadh rainfall, Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Michelsen, Nils; Reshid, Mustefa; Siebert, Christian; Schulz, Stephan; Rausch, Randolf; Knöller, Kay; Weise, Stephan; Al-Saud, Mohammed; Schüth, Christoph

    2015-04-01

    Arid countries like Saudi Arabia often depend on fossil groundwater. Hence, thorough studies of the available resources are crucial. In the course of such investigations, analyses of δ18O and δD are frequently applied to constrain the provenance of the waters and to reconstruct the (paleo)climatic conditions during their recharge. Yet, to be able to evaluate the isotopic signature of the groundwater, one also has to know the isotopic composition of current precipitation. Although a few rain water analyses are available for Central Saudi Arabia in the literature - mostly in unpublished consultant reports - a Local Meteoric Water Line has never been established. To complement the available data, 28 rain events occurring in Riyadh between 2009 and 2013 were studied for their stable isotope composition. Samples were collected as integral samples, i.e., they represent the entire precipitation event. Moreover, one event was sampled several times, aiming at an evaluation of intra-storm variability. During selected storms, a grab sample was taken for 3H analysis. The event samples showed δ18O and δD values scattering between -6.5 and +9.5 and between -30 and +50 ‰ V-SMOW, respectively. In the course of the event that was sequentially sampled, a proceeding isotopic depletion was observed with respect to both isotopes. The relatively large ranges of δ-values for 18O and D of approximately 7 and 38 ‰ V-SMOW highlight the general need for integral sampling. The obtained grab samples are characterized by moderate 3H concentrations of a few Tritium Units. Further results will be presented and discussed in view of associated weather data (e.g. rain amount and temperature) and the probable moisture sources derived from back-trajectories, which were calculated using HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory Model; Draxler & Rolph, 2003). References Draxler, R.R. & Rolph, G.D. (2013): HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory

  17. Oxygen isotopic compositions of chondrules in Allende and ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Clayton, R. N.; Mayeda, T. K.; Hutcheon, I. D.; Molini-Velsko, C.; Onuma, N.; Ikeda, Y.; Olsen, E. J.

    1983-01-01

    The ferromagnesian chondrules in Allende follow a trend in the oxygen three-isotope plot that diverges significantly from the 16-O mixing line defined by light and dark inclusions and the matrix of the meteorite. The trend probably results from isotopic exchange with an external gaseous reservoir during the process of chondrule formation sometime after the establishment of the isotopic compositions of the inclusions and matrix. The Allende chondrules approach, but do not reach, the isotopic compositions of chondrules in unequilibrated ordinary chondrites, implying exchange with a similar ambient gas, but isotopically different solid precursors for the two types of meteorite.

  18. The Lithium Isotope Composition of Planktonic Foraminifera

    NASA Astrophysics Data System (ADS)

    Hathorne, E. C.; James, R. H.; Harris, N. B.

    2003-12-01

    The temporal record of the lithium isotopic composition of seawater has the potential to provide an important proxy of the relative rates of weathering and hydrothermal processes. One of the most powerful types of evidence for changes in ocean chemistry comes from analyses of foraminiferal calcium carbonate. Here, we explore the utility of foraminifera as recorders of the Li isotopic composition of seawater. The Li isotopic composition of foraminifera tests has been determined by multicollector inductively coupled plasma mass spectrometry (Nu Instruments) using a sample-standard bracketing technique. The external precision of this technique is +/- 0.3 ‰ (2σ ), based on fifteen analyses of seawater over a period of 9 months. Planktonic foraminifera ( ˜10 mg) have been picked from surface sediments of the equatorial Pacific and the North Atlantic. Samples from the equatorial Pacific are Holocene/Pleistocene in age; those from the North Atlantic are from the Holocene. The foraminifera were subject to; cleaning in methanol and water, oxidation (hydrogen peroxide and sodium hydroxide), and leaching in weak acid (0.001M nitric acid). Additional reductive and refractory-phase cleaning steps (respectively, hydrous hydrazine/ammonia and DTPA solutions) had no effect on δ 7Li or Li/Ca. The δ 7Li value of the foraminifera ranges from 27 to 31‰ ; slightly lighter than modern-day seawater (31.1 ‰ ). Different species have consistently different δ 7Li values; O. universa have δ 7Li values within error of seawater, while Gr. truncatulinoides record the lightest δ 7Li (27.1+/- 0.3‰ ). This indicates that there are species specific vital effects on foraminiferal δ 7Li. Samples of the same species from different latitudes in the North Atlantic have the same δ 7Li, suggesting that there is no temperature effect on foraminiferal δ 7Li. Furthermore, with the exception of G. sacculifer, there appears to be no variability in foraminiferal δ 7Li with test size

  19. Nitrogen isotopic compositions of iron meteorites

    NASA Technical Reports Server (NTRS)

    Prombo, Carol A.; Clayton, Robert N.

    1993-01-01

    Iron meteorites analyzed in this study have nitrogen concentrations 70 microg/g or less and delta N-15 from -90 to +150 percent. Although the iron meteorites have a large range of delta N-15, most have values more negative than -50 percent. The nitrogen isotopic compositions were established by cosmochemical processes and were little modified by fractional crystallization or other chemical processes within the parent bodies. The data do not suggest the existence of a well-mixed solar nebular reservoir for nitrogen, as was already inferred from data from stony meteorites. The range of greater than 1100 percent observed for delta N-15 in bulk meteorites is probably too large to be accounted for by physical and chemical mass-dependent fractionation processes in the solar nebula, and thus reflects nebular inhomogeneities of nucleosynthetic origin.

  20. Magnesium Isotopic Composition of Subducting Marine Sediments

    NASA Astrophysics Data System (ADS)

    Hu, Y.; Teng, F. Z.; Plank, T. A.; Huang, K. J.

    2015-12-01

    Subducted marine sediments have recently been called upon to explain the heterogeneous Mg isotopic composition (δ26Mg, ‰) found in mantle wehrlites (-0.39 to +0.09 [1]) in the context of a homogeneous mantle (-0.25 ± 0.07 [2]). However, no systematic measurements of δ26Mg on marine sediments are currently available to provide direct support to this model. To characterize the Mg inputs to global subduction zones, we measured δ26Mg data for a total of 90 marine sediments collected from 12 drill sites outboard of the world's major subduction zones. These sediments span a 1.73‰ range in δ26Mg. The detritus-dominated sediments have δ26Mg (-0.59 to +0.53) comparable to those of weathered materials on continents (e.g. -0.52 to +0.92 [3]), while the calcareous oozes yield δ26Mg (as light as -1.20) more similar to the seawater value (-0.83 [4]). The negative correlation between δ26Mg and CaO/Al2O3 in these sediments indicates the primary control of mineralogy over the Mg isotopic distribution among different sediment types, as carbonates are enriched in light Mg isotopes (-5.10 to -0.40 [5]) whereas clay-rich weathering residues generally have heavier δ26Mg (e.g. up to +0.65 in saprolite [6]). In addition, chemical weathering and grain-size sorting drive sediments to a heavier δ26Mg, as indicated by the broad positive trends between δ26Mg with CIA (Chemical Index of Alteration [7]) and Al2O3/SiO2, respectively. Collectively, the arc systems sampled in this study represent ~30% of global arc length and the extrapolated global Mg flux of subducting marine sediments accounts for ~9% of the yearly Mg riverine input with a flux-weighted average δ26Mg at -0.26. Subduction of these heterogeneous sediments may not cause significant mantle heterogeneity on a global scale, but the highly variable Mg fluxes and δ26Mg of sediments delivered to different trenches are capable of producing local mantle variations. Volcanic rocks sourced from these mantle domains are thus

  1. A high-resolution study of isotopic compositions of precipitation

    NASA Astrophysics Data System (ADS)

    Lee, Jeonghoon; Kim, Songyi; Han, Yeongcheol; Oh, Yoon Seok; Kim, Young-Hee; Kim, Hyerin; Ham, Ji-Young; Choi, Hye-Bin; Na, Un-Sung; Koh, Dong-Chan

    2015-04-01

    Isotopic compositions of precipitation have been used to understand moisture transport in the atmosphere and interactions between precipitation and groundwater. Isotopic compositions of speleothems and ice cores, so called, "paleoarchives", can be utilized to interpret climate of the past and global circulation models (GCMs), which are able to explain the paleoarchives, can be validated by the precipitation isotopes. The developments of stable isotope analyzers make high-resolution isotopic studies feasible and a high-resolution study of precipitation isotopes is needed. For this study, precipitation samples were collected for every 5 to 15 minutes, depending on precipitation rates, using an auto-sampler for precipitation isotopes near coastal area. The isotopic compositions of precipitation range from -5.7‰ (-40.1‰)) to -10.8‰ (-74.3‰)) for oxygen (hydrogen). The slope of δ18O-δD diagram for the whole period is 6.8, but that of each storm is 5.1, 4.2, 7.9 and 7.7, respectively. It indicates that evaporation occurred during the first two storms, while the latter two storms did not experience any evaporation. The isotopic fractionations of precipitation has significant implications for the water cycle and high-resolution data of precipitation isotopes will be needed for the future studies related to the precipitation isotopes.

  2. Isotopic Composition of Barium in Single Presolar Silicon Carbide Grains

    NASA Technical Reports Server (NTRS)

    Savina, M. R.; Tripa, C. E.; Pellin, M. J.; Davis, A. M.; Clayton, R. N.; Lewis, R. S.; Amari, S.

    2002-01-01

    We have measured Ba isotope distributions in individual presolar SiC grains. We find that the Ba isotopic composition in mainstream SiC grains is consistent with models of nucleosynthesis in low to intermediate mass asymptotic giant branch (AGB) stars. Additional information is contained in the original extended abstract.

  3. Factors affecting the isotopic composition of organic matter. (1) Carbon isotopic composition of terrestrial plant materials.

    PubMed

    Yeh, H W; Wang, W M

    2001-07-01

    The stable isotope composition of the light elements (i.e., H, C, N, O and S) of organic samples varies significantly and, for C, is also unique and distinct from that of inorganic carbon. This is the result of (1) the isotope composition of reactants, (2) the nature of the reactions leading to formation and post-formational modification of the samples, (3) the environmental conditions under which the reactions took place, and (4) the relative concentration of the reactants compared to that of the products (i.e., [products]/[reactants] ratio). This article will examine the carbon isotope composition of terrestrial plant materials and its relationship with the above factors. delta13C(PDB) values of terrestrial plants range approximately from -8 to -38%, inclusive of C3-plants (-22 to -38%), C4-plants (-8 to -15%) and CAM-plants (-13 to -30%). Thus, the delta13C(PDB) values largely reflect the photosynthesis pathways of a plant as well as the genetics (i.e., species difference), delta13C(PDB) values of source CO2, relevant humidity, CO2/O2 ratios, wind and light intensity etc. Significant variations in these values also exist among different tissues, different portions of a tissue and different compounds. This is mainly a consequence of metabolic reactions. Animals mainly inherit the delta13C(PDB) values of the foods they consume; therefore, their delta13C(PDB) values are similar. The delta13C(PDB) values of plant materials, thus, contain information regarding the inner workings of the plants, the environmental conditions under which they grow, the delta13C(PDB) values of CO2 sources etc., and are unique. Furthermore, this uniqueness is passed on to their derivative matter, such as animals, humus etc. Hence, they are very powerful tools in many areas of research, including the ecological and environmental sciences.

  4. Isotopic composition of atmospheric moisture from pan water evaporation measurements.

    PubMed

    Devi, Pooja; Jain, Ashok Kumar; Rao, M Someshwer; Kumar, Bhishm

    2015-01-01

    A continuous and reliable time series data of the stable isotopic composition of atmospheric moisture is an important requirement for the wider applicability of isotope mass balance methods in atmospheric and water balance studies. This requires routine sampling of atmospheric moisture by an appropriate technique and analysis of moisture for its isotopic composition. We have, therefore, used a much simpler method based on an isotope mass balance approach to derive the isotopic composition of atmospheric moisture using a class-A drying evaporation pan. We have carried out the study by collecting water samples from a class-A drying evaporation pan and also by collecting atmospheric moisture using the cryogenic trap method at the National Institute of Hydrology, Roorkee, India, during a pre-monsoon period. We compared the isotopic composition of atmospheric moisture obtained by using the class-A drying evaporation pan method with the cryogenic trap method. The results obtained from the evaporation pan water compare well with the cryogenic based method. Thus, the study establishes a cost-effective means of maintaining time series data of the isotopic composition of atmospheric moisture at meteorological observatories. The conclusions drawn in the present study are based on experiments conducted at Roorkee, India, and may be examined at other regions for its general applicability.

  5. Ruthenium Isotopic Composition of Terrestrial Materials, Iron Meteorites and Chondrites

    NASA Technical Reports Server (NTRS)

    Becker, H.; Walker, R. J.

    2002-01-01

    Ru isotopic compositions of magmatic iron meteorites and chondrites overlap with terrestrial Ru at the 0.3 to 0.9 (epsilon) level. Additional information is contained in the original extended abstract.

  6. Isotopic compositions of the elements 2013 (IUPAC Technical Report)

    USGS Publications Warehouse

    Meija, Juris; Coplen, Tyler B.; Berglund, Michael; Brand, Willi A.; De Bièvre, Paul; Gröning, Manfred; Holden, Norman E.; Irrgeher, Johanna; Loss, Robert D.; Walczyk, Thomas; Prohaska, Thomas

    2016-01-01

    The Commission on Isotopic Abundances and Atomic Weights (ciaaw.org) of the International Union of Pure and Applied Chemistry (iupac.org) has revised the Table of Isotopic Compositions of the Elements (TICE). The update involved a critical evaluation of the recent published literature. The new TICE 2013 includes evaluated data from the “best measurement” of the isotopic abundances in a single sample, along with a set of representative isotopic abundances and uncertainties that accommodate known variations in normal terrestrial materials.

  7. The silicon isotope composition of the upper continental crust

    NASA Astrophysics Data System (ADS)

    Savage, Paul S.; Georg, R. Bastian; Williams, Helen M.; Halliday, Alex N.

    2013-05-01

    The upper continental crust (UCC) is the major source of silicon (Si) to the oceans and yet its isotopic composition is not well constrained. In an effort to investigate the degree of heterogeneity and provide a robust estimate for the average Si isotopic composition of the UCC, a representative selection of well-characterised, continentally-derived clastic sediments have been analysed using high-precision MC-ICPMS. Analyses of loess samples define a narrow range of Si isotopic compositions (δ30Si = -0.28‰ to -0.15‰). This is thought to reflect the primary igneous mineralogy and predominance of mechanical weathering in the formation of such samples. The average loess δ30Si is -0.22 ± 0.07‰ (2 s.d.), identical to average granite and felsic igneous compositions. Therefore, minor chemical weathering does not resolvably affect bulk rock δ30Si, and loess is a good proxy for the Si isotopic composition of unweathered, crystalline, continental crust. The Si isotopic compositions of shales display much more variability (δ30Si = -0.82‰ to 0.00‰). Shale Si isotope compositions do not correlate well with canonical proxies for chemical weathering, such as CIA values, but do correlate negatively with insoluble element concentrations and Al/Si ratios. This implies that more intensive or prolonged chemical weathering of a sedimentary source, with attendant desilicification, is required before resolvable negative Si isotopic fractionation occurs. Shale δ30Si values that are more positive than those of felsic igneous rocks most likely indicate the presence of marine-derived silica in such samples. Using the data gathered in this study, combined with already published granite Si isotope analyses, a weighted average composition of δ30Si = -0.25 ± 0.16‰ (2 s.d.) for the UCC has been calculated.

  8. Magnesium isotopic compositions of the Mesoproterozoic dolostones: Implications for Mg isotopic systematics of marine carbonates

    NASA Astrophysics Data System (ADS)

    Huang, Kang-Jun; Shen, Bing; Lang, Xian-Guo; Tang, Wen-Bo; Peng, Yang; Ke, Shan; Kaufman, Alan J.; Ma, Hao-Ran; Li, Fang-Bing

    2015-09-01

    Available Mg isotope data indicate that dolostones of different ages have overlapping range of Mg isotopic composition (δ26Mg) and there is no systematic difference among different types of dolomites. To further explore the Mg isotopic systematics of dolomite formation, we measured Mg isotopic compositions of Mesoproterozoic dolostones from the Wumishan Formation in North China Block, because dolomite formation in Mesoproterozoic might have been fundamentally different from the younger counterparts. Based on petrographic observations, three texturally-different dolomite phases (dolomicrite, subhedral dolomite and anhedral dolomite) are recognized in the Wumishan dolostones. Nevertheless, these three types of dolomites have similar δ26Mg values, ranging from -1.35‰ to -1.72‰, which are indistinguishable from Neoproterozoic and Phanerozoic dolostones. To explain δ26Mg values of dolostones, we simulate the Mg isotopic system during dolomite formation by applying the one-dimensional Diffusion-Advection-Reaction (1D-DAR) model, assuming that the contemporaneous seawater is the Mg source of dolostone. The 1D-DAR modeling results indicate that the degree of dolomitization is controlled by sedimentation rate, seawater Mg concentration, temperature, and reaction rate of dolomite formation, whereas Mg isotopic composition of dolostone is not only dependent on these factors, but also affected by δ26Mg of seawater and isotope fractionation during dolomite formation. Moreover, the 1D-DAR model predicts that dolomite formation within sediments has limited range of variation in δ26Mg with respect to limestones. Furthermore, the modeling results demonstrate that dolostone is always isotopically heavier than Ca-carbonate precipitated from seawater, explaining the systematic isotopic difference between dolostones and limestones. Finally, we can infer from the 1D-DAR model that early-formed dolostone at shallower depth of sediments is always isotopically lighter than that

  9. Original isotopic composition of water in precipitation by different methods

    NASA Astrophysics Data System (ADS)

    Singh, B. P.

    2016-11-01

    Stable isotopes of 2H and 18O in precipitation are different globally and carry all information about water molecules movement in hydrosphere cycles. Isotopic composition is a function of temperature, relative humidity, and speed of evaporation at different latitudes, longitudes, and altitudes. On the basis of this, we observe local meteoric water line measurements in the plot of δ2H versus δ18O. It will be interesting to know the original isotopic composition (without any modification) in a transition from cloud down to earth in different environmental conditions. This had been done by plotting of slope versus intercept of Local Meteoric Water Line (LMWL) at different altitudes in different years of observations. Intercept of LMWL with Global Meteoric Water Line (GMWL) data taken from the hydrology frame work of Corsica was plotted and it was found that the isotopic composition of water in precipitation by all these methods is same.

  10. The Palladium Isotopic Composition in Iron Meteorites

    NASA Technical Reports Server (NTRS)

    Chen, J. H.; Papanastassiou, D. A.

    2005-01-01

    Ru, Mo and Pd are very useful indicators for the identification of nucleosynthetic components. We have developed techniques for Pd isotopes, in an effort to check the extent of isotopic effects in this mass region and for a Pt-group element which is less refractory than Ru. Stable Pd isotopes are produced by the process only (102Pd), the s-process only (104Pd), the process only (Pd-110) and by both the r- and s-processes (Pd-105, Pd-106, Pd-108). Kelly and Wasserburg reported a hint of a shift in 102Pd (approx. 25(epsilon)u; 1(epsilon)u (triple bonds) 0.01%) in Santa Clara. Earlier searches for Mo and Ru isotopic anomalies were either positive or negative.

  11. Stable isotope composition of human fingernails from Slovakia.

    PubMed

    Grolmusová, Zuzana; Rapčanová, Anna; Michalko, Juraj; Čech, Peter; Veis, Pavel

    2014-10-15

    Stable isotope composition of human fingernails has proven to be useful for documenting human dietary information and geographical patterns in archeological, forensic, anthropological and biological studies. Therefore, it is of interest to detect all factors influencing the stable isotopic composition in the certain regions in the world. Carbon and nitrogen isotope data of human fingernail keratin from 52 individuals from Slovakia were reported in this study. The online combustion and continuous flow isotope-ratio mass spectrometer Delta V Advantage was used for δ(13)C and δ(15)N analysis of fingernail keratin samples from 24 vegetarian and 28 omnivorous individuals. A group of people with frequent meat consumption showed enrichment in (13)C and (15)N isotopes in fingernails. A similar trend was observed with increasing seafood in an individual's diet. Moreover a significant difference was revealed between smokers and nonsmokers for both δ(13)C and δ(15)N values. These data were compared to previously published δ(13)C and δ(15)N fingernail values from across the globe. This study brings new information on the stable isotope signature of individuals from Slovakia and characterizes the Central European region for the first time. The stable isotope composition of fingernails is influenced by the frequency of meat and seafood consumption as well as smoking.

  12. An estimate of the Germanium isotopic composition of the Ocean.

    NASA Astrophysics Data System (ADS)

    Galy, A.; Rouxel, O.; Mantoura, S.; Elderfield, H.; de La Rocha, C.

    2004-12-01

    Ge is a trace element in seawater whose biogeochemistry is dominated by its Si-like behaviour. Its residence time is poorly constrained but could be close to the mixing time of the ocean. In addition, hydrothermal vents are enriched in Ge (relative to Si) and this excess has been witnessed in the water column. Moreover, Si isotopic variations have been reported in the ocean, related to the precipitation of biogenic opal, while the Si residence time is slightly higher than the Ge residence time. Therefore, variations in the isotopic composition of dissolved Ge in the ocean are expected provided that at least one of the major input or output of Ge has a different isotopic composition. Given the low Ge concentration (around 40 picomol/kg) and the state-of-the art analytical facilities, a direct measurement of the isotopic composition of the seawater is barely conceivable. The major input of Ge into the ocean are the rivers and the hydrothermal vents, while the removal of Ge occurs through the precipitation of biogenic opal and the early diagenesis of passive margins. The mechanism of the later is, however, not well established but could be related to the precipitation of Fe-oxyhydroxide. So the measurement of marine authigenic minerals, biogenic silica and the comparison with an estimate of the bulk silicate Earth (BSE) composition will give some constraints on the Germanium isotopic composition of the ocean. A new technique for the precise and accurate determination of Ge stable isotope compositions has been developed and applied to silicate, sulfide, and biogenic material. The analyses were performed using a continuous flow hydride generation system coupled to a Nu Instrument MC-ICPMS. Samples have been purified through anion and cation exchange resins to separate Ge from matrix elements and potential interferences. Deep sea clays have a similar isotopic composition that MORBs or granites, suggesting that isotopic composition of the dissolved Ge in rivers might not

  13. The 238U/235U isotope ratio of the Earth and the solar system: Constrains from a gravimetrically calibrated U double spike and implications for absolute Pb-Pb ages

    NASA Astrophysics Data System (ADS)

    Weyer, Stefan; Noordmann, Janine; Brennecka, Greg; Richter, Stephan

    2010-05-01

    The ratio of 238U and 235U, the two primordial U isotopes, has been assumed to be constant on Earth and in the solar system. The commonly accepted value for the 238U/235U ratio, which has been used in Pb-Pb dating for the last ~ 30 years, was 137.88. Within the last few years, it has been shown that 1) there are considerable U isotope variations (~1.3‰) within terrestrial material produced by isotope fractionation during chemical reactions [1-3] and 2) there are even larger isotope variations (at least 3.5‰) in calcium-aluminum-rich inclusions (CAIs) in meoteorites that define the currently accepted age of the solar system [4]. These findings are dramatic for geochronology, as a known 238U/235U is a requirement for Pb-Pb dating, the most precise dating technique for absolute ages. As 238U/235U variations can greatly affect the reported absolute Pb-Pb age, understanding and accurately measuring variation of the 238U/235U ratio in various materials is critical, With these new findings, the questions also arises of "How well do we know the average U isotope composition of the Earth and the solar system?" and "How accurate can absolute Pb-Pb ages be?" Our results using a gravimetrically calibrated 233U/236U double spike IRMM 3636 [5] indicate that the U standard NBL 950a, which was commonly used to define the excepted "natural" 238U/235U isotope ratio, has a slightly lower 238U/235U of 137.836 ± 0.024. This value is indistinguishable from the U isotope compositions for NBL 960 and NBL112A, which have been determined by several laboratories, also using the newly calibrated U double spike IRMM 3636 [6]. These findings provide new implications about the average U isotope composition of the Earth and the solar system. Basalts display a very tight range of U isotope variations (~0.25-0.32‰ relative to SRM 950a). Their U isotope composition is also very similar to that of chondrites [4], which however appear to show a slightly larger spread. Accepting terrestrial

  14. Calcium isotopic compositions of mid-ocean ridge basalts

    NASA Astrophysics Data System (ADS)

    Zhu, H.; Zhang, Z.; Sun, W.; Wang, G. Q.

    2015-12-01

    Previous studies have demonstrated that Earth's mantle has heterogeneous calcium isotopic compositions. But the reason why mantle has its heterogeneity remains uncertain. In general, δ44/40Ca values of mantle xenolith samples have a variation of >0.45‰. While ultramafic rocks, especially dunites, have higher δ44/40Ca values than volcanic rocks, and there is a positive correlation between δ44/40Ca and Ca/Mg. These phenomena imply that the heterogeneity of Ca isotopic compositions of mantle xenolith samples might result from different degrees of melt extraction, as indicated by large Ca isotopic fractionation between co-existing clinopyroxene and orthopyroxene. However, because ancient marine carbonate has its own unique calcium isotopic characteristics, recycling of even a small amount of ancient marine carbonates into the mantle could also cause the heterogeneity of Ca isotopes in Earth's mantle. This could be the reason why oceanic island basalts (OIB) have lighter Ca isotopic compositions than the mantle xenolith. Thus, the lighter Ca isotopic compositions in the mantle source cannot only be ascribed to magmatic processes. Therefore, it is more important to know calcium isotopic characteristics during partial melting and oceanic crust contamination.Mid-ocean ridge basalts (MORB) are formed from the partial melts of the upper mantle and are rarely affected by crustal contamination. Different types of MORB, including D-MORB, N-MORB and E-MORB, have experienced different degrees of partial melting and contamination of enriched end-members. Here we report calcium isotopic characteristic of different types of MORB, we believe it will be very helpful to understand the behaviors of Ca isotopes during partial melting and it is possible to provide further information to discover the reason why calcium isotopic compositions is heterogeneous in Earth's mantle. This work was supported by Natural Science Foundation of China (No. 41373007, No. 41490632 and No. 91328204

  15. Monitoring the water vapor isotopic composition in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Sveinbjornsdottir, A. E.; Steen-Larsen, H.; Jonsson, T.; Johnsen, S. J.

    2011-12-01

    Water stable isotopes have during many decades been used as climate proxies and indicators for variations in the hydrological cycle. However we are to a great extent still using simple empirical relationships without any deeper theoretical understanding. In order to properly relate changes in the climate and hydrological cycle to changes in the observed stable water isotopic signal we must understand the underlying physical processes. Furthermore it is a challenge for General Climate Models to adequately represent the isotopes in the hydrological cycle because of lack of in-situ measurements of the atmospheric water-vapor composition in the source regions. During the fall of 2010 we installed an autonomous water vapor spectroscopy laser (from Los Gatos Research) in a lighthouse on the South Coast of Iceland (63.83 N 21.47W) with the plan to be operational for several years. The purpose of this installation was through monitoring of the water vapor isotopic composition to understand the physical processes governing the isotopic composition of the water vapor evaporated from the ocean as well as the processes of mixing between the free troposphere and marine boundary layer. Because of the remoteness of the monitoring site and simple topography we are able to isolate the 'fingerprint' on the isotopic signal in the water vapor from respectively the ocean and the interior highland leading to a near perfect case-study area. Using back-trajectories we find a strong influence of the origin of the air masses on the measured isotopic composition. The mixing of the marine-boundary layer is found to strongly influence the measured isotopic composition. The second order isotopic parameter, d-excess, is found to depend on both the isotopic composition as well as the relative humidity as prescribed by theories for evaporation from an ocean. The site likely represents a major source region for the moisture that later falls as snow on parts of the Greenland Ice Sheet. This leads to

  16. Isotopic ratio correlation for the isotopic composition analysis of plutonium in Am-Pu mixed samples having high americium content.

    PubMed

    Patra, Sabyasachi; Agarwal, Chhavi; Chaudhury, Sanhita; Newton Nathaniel, T; Gathibandhe, M; Goswami, A

    2013-08-01

    Interference of high amount of americium in the plutonium isotopic composition analysis has been studied by simulating gamma-ray spectra for Am-Pu samples over a wide composition range (5-97% (241)Am) for both power and research reactor grade plutonium. An alternate way for isotopic composition analysis has been proposed by correlating the isotopic ratios available in our old database with the experimentally obtained (241)Pu/(239)Pu isotopic ratio. The proposed method has been validated using simulated spectra of known isotopic compositions.

  17. Chromium Isotopic Compositions of Some Chondrites

    NASA Astrophysics Data System (ADS)

    Kano, N.; Imamura, M.

    1996-03-01

    Studies of isotopic anomalies in meteorites have contributed significantly to our understanding of the early history of the solar system. The isolation, identification and isotopic analysis of presolar grains in primitive meteorites has been highlight of meteoritic science in recent years and also become significant developing subdiscipline of astronomy providing primary data on stellar and supernova nucleosynthesis. We have continued detail analysis of primitive meteorites particularly acid residue fractions from them. It is because acid residues are little suffered from metamorphism due to secondary heating and shock; so they would contain the component which retains some informations on the early evolution of the solar system and on the processes of nucleosynthesis in the pre-solar stage. In this paper, we present Cr isotopic data for some chondritic meteorites and discuss the implications of the data from the viewpoint of the evolution of the solar system.

  18. Primitive boron isotope composition of the mantle.

    PubMed

    Chaussidon, M; Marty, B

    1995-07-21

    Boron isotope ratios are homogeneous in volcanic glasses of oceanic island basalts [-9.9 +/- 1.3 per mil, relative to standard NBS 951 (defined by the National Bureau of Standards)], whereas mid-oceanic ridge basalts (MORBs) and back-arc basin basalts (BABBs) show generally higher and more variable ratios. Melts that have assimilated even small amounts of altered basaltic crust show significant variations in the boron isotope ratios. Assimilation may thus account for the higher boron ratios of MORBs and BABBs. A budget of boron between mantle and crust implies that the primitive mantle had a boron isotope ratio of -10 +/- 2 per mil and that this ratio was not fractionated significantly during the differentiation of the mantle.

  19. Isotopic compositions of cometary matter returned by Stardust.

    PubMed

    McKeegan, Kevin D; Aléon, Jerome; Bradley, John; Brownlee, Donald; Busemann, Henner; Butterworth, Anna; Chaussidon, Marc; Fallon, Stewart; Floss, Christine; Gilmour, Jamie; Gounelle, Matthieu; Graham, Giles; Guan, Yunbin; Heck, Philipp R; Hoppe, Peter; Hutcheon, Ian D; Huth, Joachim; Ishii, Hope; Ito, Motoo; Jacobsen, Stein B; Kearsley, Anton; Leshin, Laurie A; Liu, Ming-Chang; Lyon, Ian; Marhas, Kuljeet; Marty, Bernard; Matrajt, Graciela; Meibom, Anders; Messenger, Scott; Mostefaoui, Smail; Mukhopadhyay, Sujoy; Nakamura-Messenger, Keiko; Nittler, Larry; Palma, Russ; Pepin, Robert O; Papanastassiou, Dimitri A; Robert, François; Schlutter, Dennis; Snead, Christopher J; Stadermann, Frank J; Stroud, Rhonda; Tsou, Peter; Westphal, Andrew; Young, Edward D; Ziegler, Karen; Zimmermann, Laurent; Zinner, Ernst

    2006-12-15

    Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild 2 particle fragments; however, extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Nonterrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single (17)O-enriched circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is (16)O-enriched, like refractory inclusions in meteorites, suggesting that Wild 2 contains material formed at high temperature in the inner solar system and transported to the Kuiper belt before comet accretion.

  20. Iron isotope composition of depleted MORB

    NASA Astrophysics Data System (ADS)

    Labidi, J.; Sio, C. K. I.; Shahar, A.

    2015-12-01

    In terrestrial basalts, iron isotope ratios are observed to weakly fractionate as a function of olivine and pyroxene crystallization. However, a ~0.1‰ difference between chondrites and MORB had been reported (Dauphas et al. 2009, Teng et al. 2013 and ref. therein). This observation could illustrate an isotope fractionation occurring during partial melting, as a function of the Fe valence in melt versus crystals. Here, we present high-precision Fe isotopic data measured by MC-ICP-MS on well-characterized samples from the Pacific-Antarctic Ridge (PAR, n=9) and from the Garrett Transform Fault (n=8). These samples allow exploring the Fe isotope fractionation between melt and magnetite, and the role of partial melting on Fe isotope fractionation. Our average δ56Fe value is +0.095±0.013‰ (95% confidence, n=17), indistinguishable from a previous estimate of +0.105±0.006‰ (95% confidence, n=43, see ref. 2). Our δ56Fe values correlate weakly with MgO contents, and correlate positively with K/Ti ratios. PAC1 DR10 shows the largest Ti and Fe depletion after titanomagnetite fractionation, with a δ56Fe value of +0.076±0.036‰. This is ~0.05‰ below other samples at a given MgO. This may illustrate a significant Fe isotope fractionation between the melt and titanomagnetite, in agreement with experimental determination (Shahar et al. 2008). GN09-02, the most incompatible-element depleted sample, has a δ56Fe value of 0.037±0.020‰. This is the lowest high-precision δ56Fe value recorded for a MORB worldwide. This basalt displays an incompatible-element depletion consistent with re-melting beneath the transform fault of mantle source that was depleted during a first melting event, beneath the ridge axis (Wendt et al. 1999). The Fe isotope observation could indicate that its mantle source underwent 56Fe depletion after a first melting event. It could alternatively indicate a lower Fe isotope fractionation during re-melting, if the source was depleted of its Fe3

  1. Verification of the isotopic composition of precipitation simulated by a regional isotope circulation model over Japan.

    PubMed

    Tanoue, Masahiro; Ichiyanagi, Kimpei; Yoshimura, Kei

    2016-01-01

    The isotopic composition (δ(18)O and δ(2)H) of precipitation simulated by a regional isotope circulation model with a horizontal resolution of 10, 30 and 50 km was compared with observations at 56 sites over Japan in 2013. All simulations produced reasonable spatio-temporal variations in δ(18)O in precipitation over Japan, except in January. In January, simulated δ(18)O values in precipitation were higher than observed values on the Pacific side of Japan, especially during an explosively developing extratropical cyclone event. This caused a parameterisation of precipitation formulation about the large fraction of precipitated water to liquid detrained water in the lower troposphere. As a result, most water vapour that transported from the Sea of Japan precipitated on the Sea of Japan side. The isotopic composition of precipitation was a useful verification tool for the parameterisation of precipitation formulation as well as large-scale moisture transport processes in the regional isotope circulation model.

  2. Zinc isotope fractionation during magmatic differentiation and the isotopic composition of the bulk Earth

    USGS Publications Warehouse

    Chen, Heng; Savage, Paul S.; Teng, Fang-Zehn; Helz, Rosalind T.; Moynier, Frédéric

    2013-01-01

    he zinc stable isotope system has been successfully applied to many and varied fields in geochemistry, but to date it is still not completely clear how this isotope system is affected by igneous processes. In order to evaluate the potential application of Zn isotopes as a proxy for planetary differentiation and volatile history, it is important to constrain the magnitude of Zn isotopic fractionation induced by magmatic differentiation. In this study we present high-precision Zn isotope analyses of two sets of chemically diverse, cogenetic samples from Kilauea Iki lava lake, Hawaii, and Hekla volcano, Iceland, which both show clear evidence of having undergone variable and significant degrees of magmatic differentiation. The Kilauea Iki samples display small but resolvable variations in Zn isotope composition (0.26‰66Zn66Zn defined as the per mille deviation of a sample's 66Zn/64Zn compositional ratio from the JMC-Lyon standard), with the most differentiated lithologies exhibiting more positive δ66Zn values. This fractionation is likely a result of the crystallization of olivine and/or Fe–Ti oxides, which can both host Zn in their crystal structures. Samples from Hekla have a similar range of isotopic variation (0.22‰66Zn66Zn=0.28±0.05‰ (2s.d.).

  3. Soil Carbon: Compositional and Isotopic Analysis

    SciTech Connect

    Moran, James J.; Alexander, M. L.; Laskin, Alexander

    2016-11-01

    This is a short chapter to be included in the next edition of the Encyclopedia of Soil Science. The work here describes techniques being developed at PNNL for investigating organic carbon in soils. Techniques discussed include: laser ablation isotope ratio mass spectrometry, laser ablation aerosol mass spectrometry, and nanospray desorption electrospray ionization mass spectrometry.

  4. Zinc isotope fractionation during magmatic differentiation and the isotopic composition of the bulk Earth

    NASA Astrophysics Data System (ADS)

    Chen, Heng; Savage, Paul S.; Teng, Fang-Zhen; Helz, Rosalind T.; Moynier, Frédéric

    2013-05-01

    The zinc stable isotope system has been successfully applied to many and varied fields in geochemistry, but to date it is still not completely clear how this isotope system is affected by igneous processes. In order to evaluate the potential application of Zn isotopes as a proxy for planetary differentiation and volatile history, it is important to constrain the magnitude of Zn isotopic fractionation induced by magmatic differentiation. In this study we present high-precision Zn isotope analyses of two sets of chemically diverse, cogenetic samples from Kilauea Iki lava lake, Hawaii, and Hekla volcano, Iceland, which both show clear evidence of having undergone variable and significant degrees of magmatic differentiation. The Kilauea Iki samples display small but resolvable variations in Zn isotope composition (0.26‰<δ66Zn<0.36‰; δ66Zn defined as the per mille deviation of a sample's 66Zn/64Zn compositional ratio from the JMC-Lyon standard), with the most differentiated lithologies exhibiting more positive δ66Zn values. This fractionation is likely a result of the crystallization of olivine and/or Fe-Ti oxides, which can both host Zn in their crystal structures. Samples from Hekla have a similar range of isotopic variation (0.22‰<δ66Zn<0.33‰), however, the degree of fractionation caused by magmatic differentiation is less significant (only 0.07‰) and no correlation between isotope composition and degree of differentiation is seen. We conclude that high temperature magmatic differentiation can cause Zn isotope fractionation that is resolvable at current levels of precision, but only in compositionally-evolved lithologies. With regards to primitive (ultramafic and basaltic) material, this signifies that the terrestrial mantle is essentially homogeneous with respect to Zn isotopes. Utilizing basaltic and ultramafic sample analyses, from different geologic settings, we estimate that the average Zn isotopic composition of Bulk Silicate Earth is δ66Zn=0.28

  5. Absolute Quantitation of Glycosylation Site Occupancy Using Isotopically Labeled Standards and LC-MS

    NASA Astrophysics Data System (ADS)

    Zhu, Zhikai; Go, Eden P.; Desaire, Heather

    2014-06-01

    N-linked glycans are required to maintain appropriate biological functions on proteins. Underglycosylation leads to many diseases in plants and animals; therefore, characterizing the extent of glycosylation on proteins is an important step in understanding, diagnosing, and treating diseases. To determine the glycosylation site occupancy, protein N-glycosidase F (PNGase F) is typically used to detach the glycan from the protein, during which the formerly glycosylated asparagine undergoes deamidation to become an aspartic acid. By comparing the abundance of the resulting peptide containing aspartic acid against the one containing non-glycosylated asparagine, the glycosylation site occupancy can be evaluated. However, this approach can give inaccurate results when spontaneous chemical deamidation of the non-glycosylated asparagine occurs. To overcome this limitation, we developed a new method to measure the glycosylation site occupancy that does not rely on converting glycosylated peptides to their deglycosylated forms. Specifically, the overall protein concentration and the non-glycosylated portion of the protein are quantified simultaneously by using heavy isotope-labeled internal standards coupled with LC-MS analysis, and the extent of site occupancy is accurately determined. The efficacy of the method was demonstrated by quantifying the occupancy of a glycosylation site on bovine fetuin. The developed method is the first work that measures the glycosylation site occupancy without using PNGase F, and it can be done in parallel with glycopeptide analysis because the glycan remains intact throughout the workflow.

  6. Measuring U-Series Isotopes in Polar Ice: Toward an Absolute Ice Chronometer

    NASA Astrophysics Data System (ADS)

    Aciego, S. M.; Bourdon, B.; Schwander, J.; Stocker, T.

    2007-12-01

    Comparison of ice records between ice sheets, alpine glaciers, and marine records currently rely on a combination of ice layer counting, matching relative time scales, and interpolation. U-series recoil from mineral aerosols (dust) into the ice matrix is one possible technique for determining the absolute age of ice, independent of any other parameters. However, the low concentrations of the U-series parents and daughters have made previous measurements difficult and the results ambiguous. We present here the first results of work we have undertaken for determining U-series recoil ages in ice cores. The primary difficulty of this technique is the extremely low concentrations of dust in polar ice samples, and therefore, of the recoil daughter products in the ice. Previous work on dust provenance indicates 0.01 to 1 mg of dust concentration per kilogram of ice from the ice cores of Greenland and Antarctica. Given these conditions, U and Th dissolved in the water fraction of the aerosol-ice system may overwhelm the total U-series budget. Constraining the possible "initial" U and Th is the first step in determining the feasibility of this dating method for ice cores. We have implemented new geochemical techniques: ultra-clean ice processing, multiple ion counter ICP-MS measurements of U and Th, and quantification of total recoveries of the aerosol and water fractions using both established USGS standards, an internal lab loess standard that best approximates the dust fraction found in ice cores, and [U]-[Th] standards SRM960 and Th105. Dissolution experiments using U and Th spikes with these standards indicate recovery of the dust and dissolved fractions are better than 99%. We present here the first concentration measurements of U from the water fraction (<0.2 microns) of freshly deposited South Pole snow (20pg/kg), as well as a series of measurements from the upper section (~128m) of the Dye 3 ice core in Greenland which thus far range from 410pg/kg to 520fg/kg U

  7. Mercury isotope compositions in North American forest soils and litters

    NASA Astrophysics Data System (ADS)

    Zheng, W.; Obrist, D.; Bergquist, B. A.

    2013-12-01

    Soils represent one of the largest reservoirs of mercury on Earth, playing a critical role in the natural cycle of mercury by acting as both a sink and source. However, it is not well understood how soils sequestrate and remobilize Hg. Natural variations in stable Hg isotopes are being explored as a promising tool in studying the transformation and transport of Hg. However, Hg isotopic data in soils is scarce. In addition, the limited isotopic data that exists is significantly different from those of atmospheric Hg, which is one of the major sources of Hg to soils. For example, Hg mass independent fractionation (MIF, typically reported as Δ199Hg) is positive in atmospheric wet deposition, but most soils display negative Δ199Hg. MIF on 200Hg (Δ200Hg) is also observed in atmospheric wet deposition, but not in soils. The discrepancy between soils and atmospheric samples is still unexplained. In this study, we surveyed the Hg isotope compositions in soil profiles, litters and fresh vegetation from four different forest sites across United States (Thompson forest, WA, Truckee, CA, Niwot Ridge, CO and Howland, MA). The current results from the WA site show that soils primarily display negative mass dependent fractionation for the even isotopes (MDF, reported as δ202Hg) with values for δ202Hg of up to -2.0‰. Significant MIF for both odd isotopes is also observed in all WA soil samples and Δ199Hg is mostly negative (up to -0.4‰). No MIF on 200Hg is observed in these soils. The negative Δ199Hg in soils is inconsistent with the positive Δ199Hg reported in atmospheric wet deposition, suggesting that either Hg transformations within or on the surface of soils and/or plants alter its isotope composition after deposition or other types of Hg deposition (e.g., Hg(0) or Hg(II) dry deposition) is more predominant. The Δ199Hg/Δ201Hg ratio is close to 1 in the soils, which is consistent with the results of laboratory photochemical reduction of inorganic Hg

  8. Chemical and isotopic compositions in acid residues from various meteorites

    NASA Technical Reports Server (NTRS)

    Kano, N.; Yamakoshi, K.; Matsuzaki, H.; Nogami, K.

    1993-01-01

    We are planning to carry out systematic isotopic investigations of Ru, Mg, etc., in primordial samples. The investigations will be pursued in the context of a study of the pre-history of the solar system. It is hoped that the study will yield direct evidence for processes of nucleosynthesis in the pre-solar stage and detection of extinct radioactive nuclides. In this paper, we present the results of chemical compositions of acid residues obtained from three types of meteorites: Canyon Diablo (IA), Allende (CV3), and Nuevo Mercuro (H5); and the preliminary results of Ru isotopic compositions.

  9. Anomalous isotopic composition of cosmic rays

    SciTech Connect

    Woosley, S.E.; Weaver, T.A.

    1980-06-20

    Recent measurements of nonsolar isotopic patterns for the elements neon and (perhaps) magnesium in cosmic rays are interpreted within current models of stellar nucleosynthesis. One possible explanation is that the stars currently responsible for cosmic-ray synthesis in the Galaxy are typically super-metal-rich by a factor of two to three. Other possibilities include the selective acceleration of certain zones or masses of supernovas or the enhancement of /sup 22/Ne in the interstellar medium by mass loss from red giant stars and planetary nebulas. Measurements of critical isotopic ratios are suggested to aid in distinguishing among the various possibilities. Some of these explanations place significant constraints on the fraction of cosmic ray nuclei that must be fresh supernova debris and the masses of the supernovas involved. 1 figure, 3 tables.

  10. The Stable Isotopic Composition of Atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Yakir, D.

    2003-12-01

    When a bean leaf was sealed in a closed chamber under a lamp (Rooney, 1988), in two hours the atmospheric CO2 in the microcosm reached an isotopic steady state with a 13C abundance astonishingly similar to the global mean value of atmospheric CO2 at that time (-7.5‰ in the δ13C notation introduced below). Almost concurrently, another research group sealed a suspension of asparagus cells in a different type of microcosm in which within about two hours the atmospheric O2 reached an isotopic steady state with 18O enrichment relative to water in the microcosm that was, too, remarkably similar to the global-scale offset between atmospheric O2 and mean ocean water (21‰ versus 23.5‰ in the δ18O notation introduced below; Guy et al., 1987). These classic experiments capture some of the foundations underlying the isotopic composition of atmospheric CO2 and O2. First, in both cases the biological system rapidly imposed a unique isotopic value on the microcosms' atmosphere via their massive photosynthetic and respiratory exchange of CO2 and O2. Second, in both cases the biological system acted on materials with isotopic signals previously formed by the global carbon and hydrological cycles. That is, the bean leaf introduced its previously formed organic matter (the source of the CO2 respired into microcosm's atmosphere), and the asparagus cells were introduced complete with local tap water (from which photosynthesis released molecular oxygen). Therefore, while the isotopic composition of the biological system used was slave to long-term processes, intense metabolic processes centered on few specific enzymes (Yakir, 2002) dictated the short-term atmospheric composition.In a similar vein, on geological timescales of millions of years, the atmosphere and its isotopic composition are integral parts of essentially a single dynamic ocean-atmosphere-biosphere system. This dynamic system exchanges material, such as carbon and oxygen, with the sediments and the lithosphere via

  11. Stable isotopic compositions in Australian precipitation

    NASA Astrophysics Data System (ADS)

    Liu, Jianrong; Fu, Guobin; Song, Xianfang; Charles, Stephen P.; Zhang, Yinghua; Han, Dongmei; Wang, Shiqin

    2010-12-01

    Stable deuterium (δD) and oxygen-18 (δ18O) isotopes in 1962 to 2002 precipitation from the seven Australian stations of the Global Network of Isotopes in Precipitation (GNIP) were used to investigate isotope characteristics including temporal and spatial distributions across different regions of Australia. On the basis of 1534 samples, the local meteoric water line (LMWL) was established as δD = 7.10δ18O + 8.21. δ18O showed a depletion trend from north and south to central Australia (a continental effect) and from west to east. Precipitation amount effects were generally greater than temperature effects, with quadratic or logarithmic correlations describing δ/T and δ/P better than linear relationships. Nonlinear stepwise regression was used to determine the significant meteorological control factors for each station, explaining about 50% or more of the δ18O variations. Geographical control factors for δ18O were given by the relationship δ18O (‰) = -0.005 longitude (°) - 0.034 latitude (°)-0.003 altitude (m) - 4.753. Four different types of d-excess patterns demonstrated particular precipitation formation conditions for four major seasonal rainfall zones. Finally, wavelet coherence (WTC) between δ18O and SOI confirmed that the influence of ENSO decreased from east and north to west Australia.

  12. Carbon isotopic composition of individual Precambrian microfossils.

    PubMed

    House, C H; Schopf, J W; McKeegan, K D; Coath, C D; Harrison, T M; Stetter, K O

    2000-08-01

    Ion microprobe measurements of carbon isotope ratios were made in 30 specimens representing six fossil genera of microorganisms petrified in stromatolitic chert from the approximately 850 Ma Bitter Springs Formation, Australia, and the approximately 2100 Ma Gunflint Formation, Canada. The delta 13C(PDB) values from individual microfossils of the Bitter Springs Formation ranged from -21.3 +/- 1.7% to -31.9 +/- 1.2% and the delta 13C(PDB) values from microfossils of the Gunflint Formation ranged from -32.4 +/- 0.7% to -45.4 +/- 1.2%. With the exception of two highly 13C-depleted Gunflint microfossils, the results generally yield values consistent with carbon fixation via either the Calvin cycle or the acetyl-CoA pathway. However, the isotopic results are not consistent with the degree of fractionation expected from either the 3-hydroxypropionate cycle or the reductive tricarboxylic acid cycle, suggesting that the microfossils studied did not use either of these pathways for carbon fixation. The morphologies of the microfossils suggest an affinity to the cyanobacteria, and our carbon isotopic data are consistent with this assignment.

  13. Carbon isotopic composition of individual Precambrian microfossils

    NASA Technical Reports Server (NTRS)

    House, C. H.; Schopf, J. W.; McKeegan, K. D.; Coath, C. D.; Harrison, T. M.; Stetter, K. O.

    2000-01-01

    Ion microprobe measurements of carbon isotope ratios were made in 30 specimens representing six fossil genera of microorganisms petrified in stromatolitic chert from the approximately 850 Ma Bitter Springs Formation, Australia, and the approximately 2100 Ma Gunflint Formation, Canada. The delta 13C(PDB) values from individual microfossils of the Bitter Springs Formation ranged from -21.3 +/- 1.7% to -31.9 +/- 1.2% and the delta 13C(PDB) values from microfossils of the Gunflint Formation ranged from -32.4 +/- 0.7% to -45.4 +/- 1.2%. With the exception of two highly 13C-depleted Gunflint microfossils, the results generally yield values consistent with carbon fixation via either the Calvin cycle or the acetyl-CoA pathway. However, the isotopic results are not consistent with the degree of fractionation expected from either the 3-hydroxypropionate cycle or the reductive tricarboxylic acid cycle, suggesting that the microfossils studied did not use either of these pathways for carbon fixation. The morphologies of the microfossils suggest an affinity to the cyanobacteria, and our carbon isotopic data are consistent with this assignment.

  14. Lithium isotope composition of basalt glass reference material.

    PubMed

    Kasemann, Simone A; Jeffcoate, Alistair B; Elliott, Tim

    2005-08-15

    We present data on the lithium isotope compositions of glass reference materials from the United States Geological Survey (USGS) and the National Institute of Standards and Technology (NIST) determined by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS), thermal ionization mass spectrometry (TIMS), and secondary ionization mass spectrometry (SIMS). Our data on the USGS basaltic glass standards agree within 2 per thousand, independent of the sample matrix or Li concentration. For SIMS analysis, we propose use of the USGS glasses GSD-1G (delta(7)Li 31.14 +/- 0.8 per thousand, 2sigma) and BCR-2G (delta(7)Li 4.08 +/- 1.0 per thousand, 2sigma) as suitable standards that cover a wide range of Li isotope compositions. Lithium isotope measurements on the silica-rich NIST 600 glass series by MC-ICPMS and TIMS agree within 0.8 per thousand, but SIMS analyses show systematic isotopic differences. Our results suggest that SIMS Li isotope analyses have a significant matrix bias in high-silica materials. Our data are intended to serve as a reference for both microanalytical and bulk analytical techniques and to improve comparisons between Li isotope data produced by different methodologies.

  15. On the nitrogen isotope composition of the solar nebula

    NASA Astrophysics Data System (ADS)

    Marty, B.; Burnard, P.; Chaussidon, M.; Hashizume, K.; Wieler, R.; Zimmermann, L.

    The two isotopes of nitrogen, 14 N and 15 N, have relative abundances extremely variable among solar system reservoirs such as planets and their atmospheres, primitive and differentiated meteorites, comets. Based on nitrogen isotope variations in lunar soil grains on one hand 1 , and on the in-situ analysis of the Jovian atmosphere on another hand 2 , it has been proposed that the Sun is depleted in 15 N by ˜ 30 % or more, whereas planetary bodies are enriched in 15 N due to incorporation of 15 N-rich compounds carried by e.g., organics. The Sun represents 99 % of the solar system mass and is probably our best representative of the solar nebula. The origin of the 15 N enrichment of the non-solar component is unclear. Isotope fractionation at low temperature during ion-molecule reaction in the interstellar medium has been proposed but apparently the magnitude of the effect cannot fully account for the range of N isotope ratios observed in the solar system. Other possibilities include isotopic effects during irradiation of the solar nebula by a very active young Sun as recently proposed to account for extreme oxygen isotope effects recorded in meteoritic organics 3 . Up to now, the exact isotopic composition of solar nitrogen as well as possible isotopic fractionation upon different solar wind regimes are not known. This constitutes one of the top priorities of the Genesis mission aimed to measure the isotopic composition of the solar wind implanted at different energies in targets exposed in space for 28 months. Despite a hard landing due to a parachute opening failure, the samples are back to Earth and treated accordingly to eliminate terrestrial contamination. The CRPG team is presently developing a UV laser rastering technique coupled with ultralow background mass spectrometry to analyse N implanted in gold covering sapphire targets. We shall present our most recent developments in selectively extracting solar wind nitrogen and analysing its isotopic composition

  16. Converting isotope ratios to diet composition - the use of mixing models - June 2010

    EPA Science Inventory

    One application of stable isotope analysis is to reconstruct diet composition based on isotopic mass balance. The isotopic value of a consumer’s tissue reflects the isotopic values of its food sources proportional to their dietary contributions. Isotopic mixing models are used ...

  17. What controls the isotopic composition of Greenland surface snow?

    NASA Astrophysics Data System (ADS)

    Steen-Larsen, H. C.; Masson-Delmotte, V.; Hirabayashi, M.; Winkler, R.; Satow, K.; Prié, F.; Bayou, N.; Brun, E.; Cuffey, K. M.; Dahl-Jensen, D.; Dumont, M.; Guillevic, M.; Kipfstuhl, S.; Landais, A.; Popp, T.; Risi, C.; Steffen, K.; Stenni, B.; Sveinbjörnsdottír, A. E.

    2014-02-01

    Water stable isotopes in Greenland ice core data provide key paleoclimatic information, and have been compared with precipitation isotopic composition simulated by isotopically enabled atmospheric models. However, post-depositional processes linked with snow metamorphism remain poorly documented. For this purpose, monitoring of the isotopic composition (δ18O, δD) of near-surface water vapor, precipitation and samples of the top (0.5 cm) snow surface has been conducted during two summers (2011-2012) at NEEM, NW Greenland. The samples also include a subset of 17O-excess measurements over 4 days, and the measurements span the 2012 Greenland heat wave. Our observations are consistent with calculations assuming isotopic equilibrium between surface snow and water vapor. We observe a strong correlation between near-surface vapor δ18O and air temperature (0.85 ± 0.11‰ °C-1 (R = 0.76) for 2012). The correlation with air temperature is not observed in precipitation data or surface snow data. Deuterium excess (d-excess) is strongly anti-correlated with δ18O with a stronger slope for vapor than for precipitation and snow surface data. During nine 1-5-day periods between precipitation events, our data demonstrate parallel changes of δ18O and d-excess in surface snow and near-surface vapor. The changes in δ18O of the vapor are similar or larger than those of the snow δ18O. It is estimated using the CROCUS snow model that 6 to 20% of the surface snow mass is exchanged with the atmosphere. In our data, the sign of surface snow isotopic changes is not related to the sign or magnitude of sublimation or deposition. Comparisons with atmospheric models show that day-to-day variations in near-surface vapor isotopic composition are driven by synoptic variations and changes in air mass trajectories and distillation histories. We suggest that, in between precipitation events, changes in the surface snow isotopic composition are driven by these changes in near-surface vapor

  18. What controls the isotopic composition of Greenland surface snow?

    NASA Astrophysics Data System (ADS)

    Steen-Larsen, H. C.; Masson-Delmotte, V.; Hirabayashi, M.; Winkler, R.; Satow, K.; Prié, F.; Bayou, N.; Brun, E.; Cuffey, K. M.; Dahl-Jensen, D.; Dumont, M.; Guillevic, M.; Kipfstuhl, J.; Landais, A.; Popp, T.; Risi, C.; Steffen, K.; Stenni, B.; Sveinbjörnsdottír, A.

    2013-10-01

    Water stable isotopes in Greenland ice core data provide key paleoclimatic information, and have been compared with precipitation isotopic composition simulated by isotopically-enabled atmospheric models. However, post-deposition processes linked with snow metamorphism remain poorly documented. For this purpose, a monitoring of the isotopic composition (δ18O, δD) of surface water vapor, precipitation and samples of top (0.5 cm) snow surface has been conducted during two summers (2011-2012) at NEEM, NW Greenland. The measurements also include a subset of 17O-excess measurements over 4 days, and the measurements span the 2012 Greenland heat wave. Our observations are consistent with calculations assuming isotopic equilibrium between surface snow and water vapor. We observe a strong correlation between surface vapor δ18O and air temperature (0.85 ± 0.11 ‰ °C-1 (R = 0.76) for 2012). The correlation with air temperature is not observed in precipitation data or surface snow data. Deuterium excess (d-excess) is strongly anti-correlated with δ18O with a stronger slope for vapor than for precipitation and snow surface data. During nine 1-5 days periods between precipitation events, our data demonstrate parallel changes of δ18O and d-excess in surface snow and surface vapor. The changes in δ18O of the vapor are similar or larger than those of the snow δ18O. It is estimated that 6 to 20% of the surface snow mass is exchanged with the atmosphere using the CROCUS snow model. In our data, the sign of surface snow isotopic changes is not related to the sign or magnitude of sublimation or condensation. Comparisons with atmospheric models show that day-to-day variations in surface vapor isotopic composition are driven by synoptic weather and changes in air mass trajectories and distillation histories. We suggest that, in-between precipitation events, changes in the surface snow isotopic composition are driven by these changes in surface vapor isotopic composition. This

  19. Heavy nickel isotope compositions in rivers and the oceans

    NASA Astrophysics Data System (ADS)

    Cameron, V.; Vance, D.

    2014-03-01

    Nickel is a biologically-active trace metal whose dissolved concentration depth profiles in the ocean show nutrient-like behaviour. If the pronounced removal of nickel from the dissolved phase in the surface ocean, and its return in the deep, is associated with an isotopic fractionation nickel isotopes may be able to yield constraints on the precise biogeochemical processes involved. Here we present the first nickel isotope data for seawater along with data for the dissolved phase of rivers, one of the principal sources of nickel to the oceans. The dissolved phase of rivers exhibits substantial variability in both Ni concentration and δ60Ni: from 2.2 to 35 nmol kg-1 and +0.29 to +1.34‰, respectively. The most striking result from the nickel isotope analyses of rivers is that they are substantially heavier (by up to 1‰ for δ60Ni) than the range for silicate rocks on the continents, a finding that is analogous to that for other transition metal isotope systems. If the data presented here are close to representative of the global riverine flux, they suggest an annual input of Ni to the oceans of 3.6 × 108moles, and a discharge- and concentration-weighted δ60Ni average of +0.80‰. The relationship between Ni isotopes and concentrations shows similarities with those for other transition metal isotope systems, where the main control has been suggested to be isotopic partitioning between the dissolved phase and particulates, either in the weathering environment or during transport. In stark contrast to the rivers, the dataset for seawater is very homogeneous, with 2SD of the entire dataset being only twice the analytical reproducibility. The second main feature is that seawater is distinctly heavier in Ni isotopes than rivers. The average δ60Ni is 1.44 ± 0.15‰ (2SD), and only 2 of the 29 seawater analyses have a Ni isotopic composition that is lighter than the heaviest river. The lack of an isotopic shift associated with the drawdown of nickel concentrations

  20. The Clumped Isotope Composition of Biogenic Methane.

    NASA Astrophysics Data System (ADS)

    Sessions, A. L.; Douglas, P. M.; Eiler, J. M.; Stolper, D. A.

    2015-12-01

    The excess or lack of 13CH3D, a doubly substituted ("clumped") isotopologue of methane, relative to that expected for a random distribution of isotopes across molecules, is a function of the processes that generated the methane. For high-temperature thermogenic methane, which typically achieves internal equilibrium, an excess of 13CH3D is expected and the amount of excess can serve as a thermometer. In contrast, biogenic methane often - though not always - has a smaller excess of clumped isotopologues, and sometimes even a deficit of clumped species ("anti-clumped"). The effect presumably arises from kinetic isotope effects accompanying enzymatic reactions in the methanogenic pathway, though the particular reaction(s) has not yet been positively identified. The decrease in clumping is also known to correlate with both the reversibility of the pathway and the methane flux. In this talk, we will present recent data bearing on the origin and utility of biologic fractionations of clumped isotopologues in methane. Preliminary data suggest that methane deriving from the fermentative pathway is enriched in D-bearing isotopologues, at the same level of clumping, relative to that derived from the CO2-reductive pathway. This property offers another potential means to distinguish biogenic methane sources in the environment. Recently, we have also begun to measure the 12CH2D2 isotopologue, for which equilibrium and kinetic isotope effects are predicted to be distinct from 13CH3D. Preliminary data suggest that the combination of both doubly-substituted isotopologues will be especially useful for disentangling mixtures containing biogenic gas.

  1. Measurement of Plutonium Isotopic Composition - MGA

    SciTech Connect

    Vo, Duc Ta

    2015-08-21

    In this module, we will use the Canberra InSpector-2000 Multichannel Analyzer with a high-purity germanium detector (HPGe) and the MGA isotopic anlysis software to assay a variety of plutonium samples. The module provides an understanding of the MGA method, its attributes and limitations. You will assess the system performance by measuring a range of materials similar to those you may assay in your work. During the final verification exercise, the results from MGA will be combined with the 240Pueff results from neutron coincidence or multiplicity counters so that measurements of the plutonium mass can be compared with the operator-declared (certified) values.

  2. Isotopic composition of transpiration and rates of change in leaf water isotopologue storage in response to environmental variables.

    PubMed

    Simonin, Kevin A; Roddy, Adam B; Link, Percy; Apodaca, Randy; Tu, Kevin P; Hu, Jia; Dawson, Todd E; Barbour, Margaret M

    2013-12-01

    During daylight hours, the isotope composition of leaf water generally approximates steady-state leaf water isotope enrichment model predictions. However, until very recently there was little direct confirmation that isotopic steady-state (ISS) transpiration in fact exists. Using isotope ratio infrared spectroscopy (IRIS) and leaf gas exchange systems we evaluated the isotope composition of transpiration and the rate of change in leaf water isotopologue storage (isostorage) when leaves were exposed to variable environments. In doing so, we developed a method for controlling the absolute humidity entering the gas exchange cuvette for a wide range of concentrations without changing the isotope composition of water vapour. The measurement system allowed estimation of (18)O enrichment both at the evaporation site and for bulk leaf water, in the steady state and the non-steady state. We show that non-steady-state effects dominate the transpiration isoflux even when leaves are at physiological steady state. Our results suggest that a variable environment likely prevents ISS transpiration from being achieved and that this effect may be exacerbated by lengthy leaf water turnover times due to high leaf water contents.

  3. A reconnaissance of the boron isotopic composition of tourmaline

    SciTech Connect

    Swihart, G.H.; Moore, P.B. )

    1989-04-01

    A preliminary investigation of the boron isotopic composition of tourmaline from some boron-rich associations has been made. The results for tourmaline from metasedimentary paragneisses (n = 12) range from {delta}{sup 11}B = {minus}22 to +22 per mil. These data mainly fall between the boron isotopic compositions of normal marine sediments with {delta}{sup 11}B = {minus}2 to +5 per mil and seawater with {delta}{sup 11}B = +39.5 per mil. Tourmaline samples from granitic pegmatites (n = 6), on the other hand, range from {delta}{sup 11}B = {minus}12 to {minus}5 per mil. The data provide a rudimentary indication of the range of boron isotopic variation in tourmaline, some of the processes leading to this range, and some possible geochemical tracer applications.

  4. H-Isotopic Composition of Apatite in Northwest Africa 7034

    NASA Technical Reports Server (NTRS)

    McCubbin, F. M.; Barnes, J. J.; Santos, A. R.; Boyce, J. W.; Anand, M.; Franchi, I. A.; Agee, C. B.

    2016-01-01

    Northwest Africa (NWA) 7034 and its pairings comprise a regolith breccia with a basaltic bulk composition [1] that yields a better match than any other martian meteorite to estimates of Mars' bulk crust composition [1]. Given the similarities between NWA 7034 and the martian crust, NWA 7034 may represent an important sample for constraining the crustal composition of components that cannot be measured directly by remote sensing. In the present study, we seek to constrain the H isotopic composition of the martian crust using Cl-rich apatite in NWA 7034.

  5. Isotopic composition of winter precipitation in Altai foothills

    NASA Astrophysics Data System (ADS)

    Malygina, N. S.; Eirich, A. N.; Papina, T. S.

    2016-11-01

    In recent years, some general circulation models have been improved by using stable water isotopologues, such as HDO (δD) and H2 18O (δ18O). In this paper, the results of a study of the isotopic composition of precipitation sampled in the winter seasons of 2014-2015 and 2015-2016 in Altai foothills are presented. The isotopic composition varied greatly: from -17.4 ‰ to -30.63 ‰ for δ18O and from -132.1 ‰ to -235.0 ‰ for δD in 2014-2015; from -15.9 %„ to -26.8 ‰ for δ18D and from -118.5 ‰ to -207.7 ‰ for δD in 2015-2016. The weighted average values of δ18O and δD for both seasons were close to each other (-21.2 ‰ and -160.1 ‰ for the first season and -20.4 ‰ and -157.5 ‰ for the second season), while the values of dexc differed significantly. A trajectory analysis (by the Hybrid Single Particle Lagrangian Integrated Trajectory - (HYSPLIT) model) has shown that the difference in the isotopic composition of the precipitation is largely associated with the change of the main source regions of atmospheric moisture, namely, the change of the North Atlantic waters (the 2014-2015 winter season) for the inland waters (the 2015-2016 winter season). A comparison of the results of an isotopic analysis has shown good agreement with data of the Global Network of Isotopes in Precipitation (GNIP) interpolated for 1960-2010. Thus, with a proper interpretation the data of the isotopic composition of the winter precipitation in Altai foothills can be used for this territory as an alternative source of the GNIP network data.

  6. The isotopic composition of enriched Si: a data analysis

    NASA Astrophysics Data System (ADS)

    Bulska, E.; Drozdov, M. N.; Mana, G.; Pramann, A.; Rienitz, O.; Sennikov, P.; Valkiers, S.

    2011-04-01

    To determine the Avogadro constant by counting the atoms in quasi-perfect spheres made of a silicon crystal highly enriched with 28Si, the isotopic composition of the crystal was measured in different laboratories by different measurement methods. This paper examines the consistency of the measurement results.

  7. Authentication of bell peppers using boron and strontium isotope compositions

    NASA Astrophysics Data System (ADS)

    Rosner, Martin; Pritzkow, Wolfgang; Vogl, Jochen; Voerkelius, Susanne

    2010-05-01

    The wrong declaration of food in terms of geographical origin and production method is a major problem for the individual consumer and public regulatory authorities. The authentication of food matrices using H-C-N-O-S isotopic compositions is already well established. However, specific questions require additional isotopic systems, which are more diagonstic for the source reservoires involved or production methods used. Here we present B and Sr isotopic compositions of bell peppers from Europe (Germany, Austria, Netherlands, Spain) and Israel to verfiy their origin. The bell peppers' B isotopic compositions between different locations are highly variable (d11BNISTSRM951 -8 to +35 ‰), whereas the 87Sr/86Sr ratios are all close to modern seawater Sr isotopic composition of about 0.7092 (0.7078 to 0.7107), but still can reliably be distinguished. Distinct isotopically heavy and light B isotopic fingerprints are obtained for bell peppers from Israel and the Netherlands. Samples from Germany, Austria, and Spain display overlapping d11B values between 0 and +12 ‰. Bell peppers from Israel show high d11B values (+28 to +35 ‰) combined with 87Sr/86Sr ratios slightly more unradiogenic than modern seawater (ca 0.7079). Bell peppers from the Netherlands, however, show low d11B values (-8 ‰) combinded with 87Sr/86Sr ratios of modern seawater (approx. 0.7085). Mainly based on diagnostic B isotopic compositions bell peppers from Israel and the Netherlands can be related to a specific geographical growing environment (Israel) or production method (Netherlands). The isotope fingerprints of bell peppers from the Netherlands are consistent with growing conditions in greenhouses typical for the Netherlands vegetable farming. Using optimized production methods crops in greenhouses were supplied with nutritients by liquid fertilizers on artificial substrates. As most fertilizers derive from non-marine salt deposits, fertilization typically imprints invariant d11B values close

  8. Hydrogen Isotopic Composition of Hornblendes From Active Volcanoes of Mexico

    NASA Astrophysics Data System (ADS)

    Taran, Y.; Kusakabe, M.; Valdez, G.; Mora, J. C.

    2002-12-01

    Horblendes (Hb) crystallize in water-rich magmas in magma chambers or in deeper zones. Isotopic composition of hydrogen in OH-groups of Hb represents the water isotopic composition of magmatic fluid or dissolved magmatic volatiles and therefore, is an isotopic characteristics of magmatic water. At lower vapor pressure in conduits and shallower magma chambers, Hb can decompose and loose water with significant isotopic effects. We measured hydrogen isotopic composition of hornblendes from modern lavas and pyroclastics of El Chichon, Colima and Popocatepetl volcanoes. Hornblendes from the last and previous pyroclastic flows of El Chichon are the more abundant mineral phases (after plagioclase), showing pleochroism from green to brown. They are relatively uniform in composition (close to magnesian hastingsite hornblende), without chemical variations between cores and rims. Using the Johnson and Rutherford (1989) calibration of the Al-in-hornblende geobarometer, the hornblendes show equilibrium with the melt at pressure of 4 kb that correspond to 12 km of depth. These pressure conditions likely represent the location of the magma chamber below El Chichon volcano, however, these pressure estimates need to be confirmed. The water content of all analyzed Hbs is 1.5-1.8 wt%, but may be higher due to a minor amount of impurities of pyroxenes which sometimes are difficult to separate from Hb. Hydrogen isotopic composition in 10 samples of Hb from El Chichon of different age and facies (pumice, lithic fragments in pyroclastics) was in a narrow range -40 to -37 permil V-SMOW. Such isotopic signature corresponds to so-called "andesitic" waters, i.e. waters from subduction-related magmas, The origin of these waters is suggested to be the recycled water from subducted oceanic sediments. The data for El Chichon volcano are in the range of the already known values for subduction-related magmas though the tectonic setting of El Chichon is more complicated. The measured isotopic

  9. Isotope composition and volume of Earth's early oceans.

    PubMed

    Pope, Emily C; Bird, Dennis K; Rosing, Minik T

    2012-03-20

    Oxygen and hydrogen isotope compositions of Earth's seawater are controlled by volatile fluxes among mantle, lithospheric (oceanic and continental crust), and atmospheric reservoirs. Throughout geologic time the oxygen mass budget was likely conserved within these Earth system reservoirs, but hydrogen's was not, as it can escape to space. Isotopic properties of serpentine from the approximately 3.8 Ga Isua Supracrustal Belt in West Greenland are used to characterize hydrogen and oxygen isotope compositions of ancient seawater. Archaean oceans were depleted in deuterium [expressed as δD relative to Vienna standard mean ocean water (VSMOW)] by at most 25 ± 5‰, but oxygen isotope ratios were comparable to modern oceans. Mass balance of the global hydrogen budget constrains the contribution of continental growth and planetary hydrogen loss to the secular evolution of hydrogen isotope ratios in Earth's oceans. Our calculations predict that the oceans of early Earth were up to 26% more voluminous, and atmospheric CH(4) and CO(2) concentrations determined from limits on hydrogen escape to space are consistent with clement conditions on Archaean Earth.

  10. CALCIUM ISOTOPE COMPOSITION OF METEORITES, EARTH, AND MARS

    SciTech Connect

    Simon, Justin I.; DePaolo, Donald J.; Moynier, Frederic

    2009-09-01

    The relative abundances of calcium isotopes in the mass range 40-44 were measured in primitive and differentiated meteorites and igneous rocks from Earth and Mars in search of non-mass-dependent variations that could provide clues about early solar system processes. Most bulk samples of planetary materials have calcium isotopic compositions identical with Earth's within the current resolution of about 0.01% in {sup 40}Ca/{sup 44}Ca. Possible exceptions include carbonaceous chondrites, some ordinary chondrites, and two samples of calcium-aluminum-rich inclusions, which have small excesses of {sup 40}Ca. The samples with {sup 40}Ca excesses are also known to have {sup 50}Ti and {sup 135}Ba excesses and {sup 142}Nd and {sup 144}Sm deficits. Collectively these data from refractory elements suggest that the planetary embryos represented by chondrites preserve isotopic heterogeneity that reflects different nucleosynthetic sources. No late admixture from a single nucleosynthetic source can explain all observations. The results are most compatible with variable proportions of material derived from Type II supernovae. The initial calcium isotope compositions of Earth and Mars are indistinguishable and similar to the {sup 40}Ca abundance found in some chondrites and all differentiated meteorites studied. It appears that isotopic heterogeneity in calcium was still present at the completion of disk formation but was homogenized during planetary accretion.

  11. Isotope composition and volume of Earth’s early oceans

    PubMed Central

    Pope, Emily C.; Bird, Dennis K.; Rosing, Minik T.

    2012-01-01

    Oxygen and hydrogen isotope compositions of Earth’s seawater are controlled by volatile fluxes among mantle, lithospheric (oceanic and continental crust), and atmospheric reservoirs. Throughout geologic time the oxygen mass budget was likely conserved within these Earth system reservoirs, but hydrogen’s was not, as it can escape to space. Isotopic properties of serpentine from the approximately 3.8 Ga Isua Supracrustal Belt in West Greenland are used to characterize hydrogen and oxygen isotope compositions of ancient seawater. Archaean oceans were depleted in deuterium [expressed as δD relative to Vienna standard mean ocean water (VSMOW)] by at most 25 ± 5‰, but oxygen isotope ratios were comparable to modern oceans. Mass balance of the global hydrogen budget constrains the contribution of continental growth and planetary hydrogen loss to the secular evolution of hydrogen isotope ratios in Earth’s oceans. Our calculations predict that the oceans of early Earth were up to 26% more voluminous, and atmospheric CH4 and CO2 concentrations determined from limits on hydrogen escape to space are consistent with clement conditions on Archaean Earth. PMID:22392985

  12. Controls over the strontium isotope composition of river water

    SciTech Connect

    Palmer, M.R. ); Edmond, J.M. )

    1992-05-01

    Strontium concentrations and isotope ratios have been measured in river and ground waters from the Granges, Orinoco, and Amazon river basins. When compared with major element concentrations, the data set has allowed a detailed examination of the controls over the strontium isotope systematics of riverine input to the oceans in the following environments: (1) typical drainage basins containing limestones, evaporites, shales, and alumino-silicate metamorphic and igneous rocks; (2) shield terrains containing no chemical or biogenic sediments; and (3) the flood plains that constitute the largest areas of many large rivers. The strontium concentration and isotope compositions of river waters are largely defined by mixing of strontium derived from limestones and evaporites with strontium derived from silicate rocks. The strontium isotope composition of the limestone end member generally lies within the Phanerozoic seawater range, which buffers the [sup 87]Sr/[sup 86]Sr ratios of major rivers. A major exception is provided by the rivers draining the Himalayas, where widescale regional metamorphism appears to have led to an enrichment in limestones of radiogenic strontium derived from coexisting silicate rocks. The strontium isotope systematics of rivers draining shield areas are controlled by the intense, transport-limited, nature of the weathering reactions, and thereby limits variations in the strontium flux from these terrains. Flood plains are only a minor source of dissolved strontium to river waters, and precipitation of soil salts in some flood plains can reduce the riverine flux of dissolved strontium to the oceans.

  13. Tracing anthropogenic thallium in soil using stable isotope compositions.

    PubMed

    Kersten, Michael; Xiao, Tangfu; Kreissig, Katharina; Brett, Alex; Coles, Barry J; Rehkämper, Mark

    2014-08-19

    Thallium stable isotope data are used in this study, for the first time, to apportion Tl contamination in soils. In the late 1970s, a cement plant near Lengerich, Germany, emitted cement kiln dust (CKD) with high Tl contents, due to cocombustion of Tl-enriched pyrite roasting waste. Locally contaminated soil profiles were obtained down to 1 m depth and the samples are in accord with a binary mixing relationship in a diagram of Tl isotope compositions (expressed as ε(205)Tl, the deviation of the (205)Tl/(203)Tl ratio of a sample from the NIST SRM 997 Tl isotope standard in parts per 10(4)) versus 1/[Tl]. The inferred mixing endmembers are the geogenic background, as defined by isotopically light soils at depth (ε(205)Tl ≈ -4), and the Tl emissions, which produce Tl-enriched topsoils with ε(205)Tl as high as ±0. The latter interpretation is supported by analyses of the CKD, which is also characterized by ε(205)Tl ≈ ± 0, and the same ε(205)Tl value was found for a pyrite from the deposit that produced the cocombusted pyrite roasting waste. Additional measurements for samples from a locality in China, with outcrops of Tl sulfide mineralization and associated high natural Tl backgrounds, reveal significant isotope fractionation between soils (ε(205)Tl ≈ +0.4) and locally grown green cabbage (ε(205)Tl between -2.5 and -5.4). This demonstrates that biological isotope fractionation cannot explain the isotopically heavy Tl in the Lengerich topsoils and the latter are therefore clearly due to anthropogenic Tl emissions from cement processing. Our results thus establish that isotopic data can reinforce receptor modeling for the toxic trace metal Tl.

  14. Stable isotopic compositions of carbon in vegetation and soil organic matter along the bioclimatic transect, North Caucasus

    NASA Astrophysics Data System (ADS)

    Kovda, Irina; Morgun, Evgeny; Golubeva, Natalia

    2010-05-01

    Stable isotopic composition of carbon in plant species and soil organic matter was investigated along the bioclimatic transect in the North Caucasus. The aim of this research was to find the possible shift of stable isotopic composition of carbon reflecting the gradual successive changes of landscapes connected with the changes of climatic conditions (temperature, precipitation, air humidity) at a various absolute heights above sea level i.e. along the vertical zonation. The study site was located in the North Caucasus near Arkhiz, Big Zelentchuk valley (43o33-40'N; 41o16-27'E). Soil and vegetation samples were collected along Precaucasus and Caucasus slopes at an absolute heights interval of 1280 - 2065 m. Soils are formed at eluvo-deluvium of noncarbonated silicate massive rocks under warm temperate climate with MAT 4-5oC and MAP ~ 860 mm and more. Samples of vegetation (whole grasses and tree leaves) represented several altitudinal vegetation belts including forest and subalpine belts with coniferous (pine, spruce, fir), mixed coniferous-deciduous (fir + beech), broad-leaved (beech, maple), small-leaved (birch, aspen) forests, elfin birch wood and subalpine meadows. Stable isotope composition of carbon was determined using IRMS Finnigan Delta V+. Stable isotopic composition of vegetal species ranges from -33.04 to -27.29 o/oo with the general trend of lighter δ13С with the decreasing of absolute heights. The most heavier δ13С = ~ -27o/oo were found in subalpine meadow plants, while at a smaller altitudes in the forest belt δ13С shifts to ~ 30-31, and up to ~ - 32-33o/oo. More clear regularities were found for vegetation specimens grouped into three categories such as "trees", "grasses" and "litter". δ13С of each category clearly shifts to the lighter values with the decrease of absolute heights i.e from subalpine meadows to spruce-broad-leaved forests. δ13С shift is about 2,49o/oo for trees, 1,75-4,92 o/oo for grasses and ~ 1,8 o/oo for the litter. The

  15. The abundance and isotopic composition of water in eucrites

    NASA Astrophysics Data System (ADS)

    Barrett, T. J.; Barnes, J. J.; TartèSe, R.; Anand, M.; Franchi, I. A.; Greenwood, R. C.; Charlier, B. L. A.; Grady, M. M.

    2016-06-01

    Volatile elements play a key role in the dynamics of planetary evolution. Extensive work has been carried out to determine the abundance, distribution, and source(s) of volatiles in planetary bodies such as the Earth, Moon, and Mars. A recent study showed that the water in apatite from eucrites has similar hydrogen isotopic compositions compared to water in terrestrial rocks and carbonaceous chondrites, suggesting that water accreted very early in the inner solar system given the ancient crystallization ages (~4.5 Ga) of eucrites. Here, the measurements of water (reported as equivalent H2O abundances) and the hydrogen isotopic composition (δD) of apatite from five basaltic eucrites and one cumulate eucrite are reported. Apatite H2O abundances range from ~30 to ~3500 ppm and are associated with a weighted average δD value of -34 ± 67‰. No systematic variations or correlations are observed in H2O abundance or δD value with eucrite geochemical trend or metamorphic grade. These results extend the range of previously published hydrogen isotope data for eucrites and confirm the striking homogeneity in the H-isotopic composition of water in eucrites, which is consistent with a common source for water in the inner solar system.

  16. The Chlorine Isotopic Composition Of Lunar UrKREEP

    NASA Technical Reports Server (NTRS)

    Barnes, J. J.; Tartese, R.; Anand, M.; McCubbin, F. M.; Neal, C. R.; Franchi, I. A.

    2016-01-01

    Since the long standing paradigm of an anhydrous Moon was challenged there has been a renewed focus on investigating volatiles in a variety of lunar samples. However, the current models for the Moon’s formation have yet to fully account for its thermal evolution in the presence of H2O and other volatiles. When compared to chondritic meteorites and terrestrial rocks, lunar samples have exotic chlorine isotope compositions, which are difficult to explain in light of the abundance and isotopic composition of other volatile species, especially H, and the current estimates for chlorine and H2O in the bulk silicate Moon. In order to better understand the processes involved in giving rise to the heavy chlorine isotope compositions of lunar samples, we have performed a comprehensive in situ high precision study of chlorine isotopes, using NanoSIMS (Nanoscale Secondary Ion Mass Spectrometry) of lunar apatite from a suite of Apollo samples covering a range of geochemical characteristics and petrologic types.

  17. Menopause effect on blood Fe and Cu isotope compositions.

    PubMed

    Jaouen, Klervia; Balter, Vincent

    2014-02-01

    Iron (δ(56) Fe) and copper (δ(65) Cu) stable isotope compositions in blood of adult human include a sex effect, which still awaits a biological explanation. Here, we investigate the effect of menopause by measuring blood δ(56) Fe and δ(65) Cu values of aging men and women. The results show that, while the Fe and Cu isotope compositions of blood of men are steady throughout their lifetime, postmenopausal women exhibit blood δ(65) Cu values similar to men, and δ(56) Fe values intermediate between men and premenopausal women. The residence time of Cu and Fe in the body likely explains why the blood δ(65) Cu values, but not the δ(56) Fe values, of postmenopausal women resemble that of men. We suggest that the Cu and Fe isotopic fractionation between blood and liver resides in the redox reaction occurring during hepatic solicitation of Fe stores. This reaction affects the Cu speciation, which explains why blood Cu isotope composition is impacted by the cessation of menstruations. Considering that Fe and Cu sex differences are recorded in bones, we believe this work has important implications for their use as a proxy of sex or age at menopause in past populations.

  18. The Chlorine Isotopic Composition Of Lunar UrKREEP

    NASA Technical Reports Server (NTRS)

    Barnes, J. J.; Tartese, R.; Anand, M.; McCubbin, F. M.; Neal, C. R.; Franchi, I. A.

    2016-01-01

    Since the long standing paradigm of an anhydrous Moon was challenged there has been a renewed focus on investigating volatiles in a variety of lunar samples. Numerous studies have examined the abundances and isotopic compositions of volatiles in lunar apatite, Ca5(PO4)3(F,Cl,OH). In particular, apatite has been used as a tool for assessing the sources of H2O in the lunar interior. However, current models for the Moon's formation have yet to fully account for its thermal evolution in the presence of H2O and other volatiles. For ex-ample, in the context of the lunar magma ocean (LMO) model, it is anticipated that chlorine (and other volatiles) should have been concentrated in the late-stage LMO residual melts (i.e., the dregs enriched in incompatible elements such as K, REEs (Rare Earth Elements), and P, collectively called KREEP, and in its primitive form - urKREEP, given its incompatibility in mafic minerals like olivine and pyroxene, which were the dominant phases that crystallized early in the cumulate pile of the LMO. When compared to chondritic meteorites and terrestrial rocks, lunar samples have exotic chlorine isotope compositions, which are difficult to explain in light of the abundance and isotopic composition of other volatile species, especially H, and the current estimates for chlorine and H2O in the bulk silicate Moon (BSM). In order to better understand the processes involved in giving rise to the heavy chlorine isotope compositions of lunar samples, we have performed a comprehensive in situ high precision study of chlorine isotopes in lunar apatite from a suite of Apollo samples covering a range of geochemical characteristics and petrologic types.

  19. C-isotope composition of fossil sedges and grasses

    NASA Astrophysics Data System (ADS)

    Kurschner, Wolfram M.

    2010-05-01

    C4 plants differ from C3 plants regarding their anatomy and their C-isotope composition. Both features can be used in the geological record to determine the presence of C4 plants. Yet, the evolution of the C4 pathway in the fossil record is enigmatic as palaeobotanical and geological evidence for C4 plants is sparse. The oldest structural evidence for Kranz anatomy has been found in Late Miocene permineralized grass leaf remains. But studies on the C-isotope composition of sedimentary organic matter indicate that abundant C4 biomass was present in N-America and Asia throughout the Miocene in expanding savannahs and grasslands. The success of C4 plants appears to be related also to an increasing seasonal aridity in the tropical climate belts and the co-evolution of grazers. However, C- isotope composition of palaeosols or vertebrate teeth only allows to estimate the abundance of C4 plant biomass in the vegetation or in the diet without further taxonomical specification which plant groups would have had C4 metabolism. In this contribution the first extensive C-isotope analysis of fossil seeds of sedges and a few grasses are presented. The age of the carpological material ranges from Late Eocene to Pliocene and was collected from several central European brown coal deposits. The 52 different taxa studied include several species of Carex, Cladiocarya, Eriopherum, Eleocharis, Scirpus, Sparganium. Most of them representing herbaceous elements of a (sub)tropical vegetation growing near the edge of a lake. The C-isotope composition of the fossil seeds varies between -30 and -23 o/oo indicating C3 photosynthesis. This first systematic inventory shows that C4 plants were absent in the European (sub)tropical brown coal forming wetland vegetation during the Tertiary. These preliminary data are in agreement with phylogenetic studies which predict the origin of C4 plants outside the European realm.

  20. Do foraminifera accurately record seawater neodymium isotope composition?

    NASA Astrophysics Data System (ADS)

    Scrivner, Adam; Skinner, Luke; Vance, Derek

    2010-05-01

    Palaeoclimate studies involving the reconstruction of past Atlantic meridional overturning circulation increasingly employ isotopes of neodymium (Nd), measured on a variety of sample media (Frank, 2002). In the open ocean, Nd isotopes are a conservative tracer of water mass mixing and are unaffected by biological and low-temperature fractionation processes (Piepgras and Wasserburg, 1987; Lacan and Jeandel, 2005). For decades, benthic foraminifera have been widely utilised in stable isotope and geochemical studies, but have only recently begun to be exploited as a widely distributed, high-resolution Nd isotope archive (Klevenz et al., 2008), potentially circumventing the difficulties associated with other methods used to recover past deep-water Nd isotopes (Klevenz et al., 2008; Rutberg et al., 2000; Tachikawa et al., 2004). Thus far, a single pilot study (Klevenz et al., 2008) has indicated that core-top sedimentary benthic foraminifera record a Nd isotope composition in agreement with the nearest available bottom seawater data, and has suggested that this archive is potentially useful on both millennial and million-year timescales. Here we present seawater and proximal core-top foraminifer Nd isotope data for samples recovered during the 2008 "RETRO" cruise of the Marion Dufresne. The foraminifer samples comprise a depth-transect spanning 3000m of the water column in the Angola Basin and permit a direct comparison between high-resolution water column and core-top foraminiferal Nd isotope data. We use these data to assess the reliability of both planktonic and benthic foraminifera as recorders of water column neodymium isotope composition. Frank, M., 2002. Radiogenic isotopes: Tracers of past ocean circulation and erosional input, Rev. Geophys., 40 (1), 1001, doi:10.1029/2000RG000094. Klevenz, V., Vance, D., Schmidt, D.N., and Mezger, K., 2008. Neodymium isotopes in benthic foraminifera: Core-top systematics and a down-core record from the Neogene south Atlantic

  1. The Li isotope composition of modern biogenic carbonates

    NASA Astrophysics Data System (ADS)

    Dellinger, M.; West, A. J.; Adkins, J. F.; Paris, G.; Eagle, R.; Freitas, P. S.; Bagard, M. L.; Ries, J. B.; Corsetti, F. A.; Pogge von Strandmann, P.; Ullmann, C. V.

    2015-12-01

    The lithium stable isotope composition (δ7Li) of sedimentary carbonates has great potential to unravel weathering rates and intensity in the past, with implications for understanding the carbon cycle over geologic time. However, so far very little is known about the potential influence of fractionation of the stable Li isotope composition of biogenic carbonates. Here, we investigate the δ7Li of various organisms (particularly mollusks, echinoderms and brachiopods) abundant in the Phanerozoic record, in order to understand which geologic archives might provide the best targets for reconstructing past seawater composition. The range of measured samples includes (i) modern calcite and aragonite shells from variable natural environments, (ii) shells from organisms grown under controlled conditions (temperature, salinity, pCO2), and (iii) fossil shells from a range of species collected from Miocene deposits. When possible, both the inner and outer layers of bivalves were micro-sampled to assess the intra-shell heterogeneity. For calcitic shells, the measured δ7Li of bivalve species range from +32 to +41‰ and is systematically enriched in the heavy isotope relative to seawater (31 ‰) and to inorganic calcite, which is characterized by Δ7Licalcite-seawater = -2 to -5‰ [1]. The Li isotope composition of aragonitic bivalves, ranging from +16 to +22‰, is slightly fractionated to both high and low δ7Li relative to inorganic aragonite. The largest intra-shell Li isotope variability is observed for mixed calcite-aragonite shells (more than 20‰) whereas in single mineralogy shells, intra-shell δ7Li variability is generally less than 3‰. Overall, these results suggest a strong influence of vital effects on Li isotopes during bio-calcification of bivalve shells. On the contrary, measured brachiopods systematically exhibit fractionation that is very similar to inorganic calcite, with a mean δ7Li of 27.0±1.5‰, suggesting that brachiopods may provide good

  2. Unnatural Isotopic Composition of Lithium Reagents

    USGS Publications Warehouse

    Qi, H.P.; Coplen, T.B.; Wang, Q. Zh; Wang, Y.-H.

    1997-01-01

    Isotopic analysis of 39 lithium reagents from several manufacturers indicates that seven were artificially depleted in 6Li significantly in excess of the variation found in terrestrial materials. The atomic weight of lithium in analyzed reagents ranged from 6.939 to 6.996, and ??7-Li, reported relative to L-SVEC lithium carbonate, ranged from -11 to +3013???. This investigation indicates that 6Li-depleted reagents are now found on chemists' shelves, and the labels of these 6Li-depleted reagents do not accurately reflect the atomic and (or) molecular weights of these reagents. In 1993, IUPAC issued the following statement: "Commercially available Li materials have atomic weights that range between 6.94 and 6.99; if a more accurate value is required, it must be determined for the specific material." This statement has been found to be incorrect In two of the 39 samples analyzed, the atomic weight of Li was in excess of 6.99.

  3. Boron isotopic compositions of some boron minerals

    SciTech Connect

    Oi, Takao; Musashi, Masaaki; Ossaka, Tomoko; Kakihana, Hidetake ); Nomura, Masao; Okamoto, Makoto )

    1989-12-01

    Boron minerals that have different structural formulae but are supposed to have the same geologic origin have been collected and analyzed for the {sup 11}B/{sup 10}B isotopic ratio. It has been reconfirmed that minerals of marine origin have higher {sup 11}B/{sup 10}B ratios than those of nonmarine origin. It has been found that the sequence of decreasing {sup 11}B/{sup 10}B values among the minerals with the same geologic origin is; borax, tincal, kernite (Na borates) > ulexite (Na/Ca borate) > colemanite, iyoite, meyerhofferite (Ca borates). This sequence is explainable on the basis of the difference in crystal structure among the minerals. That is, minerals with high BO{sub 3}/BO{sub 4} ratios, (the ratio of the number of the BO{sub 3} triangle units to the number of the BO{sub 4} tetrahedron units in the structural formula of a mineral) have higher {sup 11}B/{sup 10}B ratios.

  4. Effect of Plant Uptake on Perchlorate Isotopic Composition

    NASA Astrophysics Data System (ADS)

    Estrada, N. L.; Jackson, W. A.; Bohlke, J. K.; Sturchio, N. C.; Gu, B.; Rao, B.; Hatzinger, P. B.; Harvey, G.; Burkey, K.; McGrath, M. T.; Sevanthi, R.

    2013-12-01

    The occurrence of perchlorate (ClO4-) in the environment is attributed to both synthetic and natural sources. Unlike anthropogenic ClO4-, natural ClO4- exhibits a wide range in isotopic compositions, suggesting that natural ClO4- is formed through more than one pathway and/or undergoes post-depositional isotopic fractionation processes. One of these processes could be plant uptake and metabolism. Plants are known to reversibly accumulate ClO4-. However, there is little information available regarding the ability for plants to isotopically fractionate ClO4-. Plants could alter ClO4-isotopic composition either by mass dependent fractionation via transport carriers in the root, diffusion limitations through the root, translocation within the plant, reduction of ClO4- by plant enzymes, or non-specific exchange of oxygen in ClO4- catalyzed by plant compounds/processes. We examined the potential for plants to alter the isotopic composition of ClO4- (δ37Cl, δ18O, and Δ17O) in both hydroponic and field scale experiments. Hydroponically grown snap bean plants were exposed to variable ClO4-concentrations (2mg/L and 10mg/L) in solutions prepared from ClO4- with both normal and anomalous O isotopic abundances. At maturity, we evaluated the uptake of ClO4-relative to other anions and the isotopic compositions of ClO4- in both plants and growth solutions. Additional experiments involved field scale exposures of snap beans to irrigation water containing low levels (< 10 ug/L) of ClO4-. The majority of the initial mass of ClO4- for both the low and high exposure hydroponic treatments was recovered in the growth solutions (20-40%) or plant compartments (40-60%), while some mass was not recovered (~20%). ClO4- isotopic compositions were essentially identical between recovered ClO4- in the plant tissues and hydroponic solutions. Anion ratios indicate that ClO4-was accumulated similarly to NO3- but preferentially to Cl- (~4X). In field experiments, the isotopic composition of ClO4

  5. Stable isotopic composition of bottled mineral waters from Romania

    NASA Astrophysics Data System (ADS)

    Bădăluţă, Carmen; Nagavciuc, Viorica; Perșoiu, Aurel

    2015-04-01

    Romania has a high potential of mineral waters resources, featuring one of the largest mineral resources at European and global level. In the last decade, due to increased in consumption of bottled water, numerous brands have appeared on the market, with equally numerous and variable sources of provenance. In this study we have analyzed the isotopic composition of bottled mineral waters from Romania in order to determine their source and authenticity. We have analysed 32 carbonated and 24 non-carbonated mineral waters from Romania. and the results were analysed in comparison with stable isotope data from precipitation and river waters. Generally, the isotopic values of the mineral waters follow those in precipitation; however, differences occur in former volcanic regions (due to deep circulation of meteoric waters and increased exchange with host rock and volcanic CO2), as well as in mountainous regions, where high-altitude recharge occurs.

  6. Osmium Isotope and Highly Siderophile Element Compositions of Lunar Orange and Green Glasses

    NASA Technical Reports Server (NTRS)

    Walker, R. J.; Horan, M. F.; Shearer, C. K.; Papike, J. J.

    2003-01-01

    The absolute and relative abundances of the highly siderophile elements (HSE) present in planetary mantles are primarily controlled by: 1) silicate-metal partitioning during core-mantle differentiation, 2) the subsequent addition of HSE to mantles via continued planetary accretion. Consequently, constraints on the absolute and relative abundances of the HSE in the lunar mantle will provide unique insights to the formation and late accretionary history of not only the Moon, but also Earth. Determining the HSE content of the lunar mantle, however, has proven difficult, because no bona fide mantle rocks have been collected from the moon. The only materials presently available for constraining mantle abundances are lunar volcanic rocks. Lunar basalts typically have very low concentrations of HSE and highly fractionated HSE patterns. Because of our extremely limited understanding of mantle melt partitioning of the HSE, even for terrestrial systems, extrapolations to mantle compositions from basaltic compositions are difficult, except possibly for the less compatible HSE Pt and Pd. Primitive, presumably less fractionated materials, such as picritic glasses are potentially more diagnostic of the lunar interior. Here we report Os isotopic composition data and Re, Os, Ir, Ru, Pt and Pd concentration data for green glass (15426,164) and orange glass (74001,1217). As with previous studies utilizing neutron activation analysis, we are examining different size fractions of the spherules to assess the role of surface condensation in the generation of the HSE abundances.

  7. The chromium isotope composition of reducing and oxic marine sediments

    NASA Astrophysics Data System (ADS)

    Gueguen, Bleuenn; Reinhard, Christopher T.; Algeo, Thomas J.; Peterson, Larry C.; Nielsen, Sune G.; Wang, Xiangli; Rowe, Harry; Planavsky, Noah J.

    2016-07-01

    The chromium (Cr) isotope composition of marine sediments has the potential to provide new insights into the evolution of Earth-surface redox conditions. There are significant but poorly constrained isotope fractionations associated with oxidative subaerial weathering and riverine transport, the major source of seawater Cr, and with partial Cr reduction during burial in marine sediments, the major sink for seawater Cr. A more comprehensive understanding of these processes is needed to establish global Cr isotope mass balance and to gauge the utility of Cr isotopes as a paleoredox proxy. For these purposes, we investigated the Cr isotope composition of reducing sediments from the upwelling zone of the Peru Margin and the deep Cariaco Basin. Chromium is present in marine sediments in both detrital and authigenic phases, and to estimate the isotopic composition of the authigenic fraction, we measured δ53Cr on a weakly acid-leached fraction in addition to the bulk sediment. In an effort to examine potential variability in the Cr isotope composition of the detrital fraction, we also measured δ53Cr on a variety of oxic marine sediments that contain minimal authigenic Cr. The average δ53Cr value of the oxic sediments examined here is -0.05 ± 0.10‰ (2σ, n = 25), which is within the range of δ53Cr values characteristic of the bulk silicate Earth. This implies that uncertainty in estimates of authigenic δ53Cr values based on bulk sediment analyses is mainly linked to estimation of the ratio of Cr in detrital versus authigenic phases, rather than to the Cr-isotopic composition of the detrital pool. Leaches of Cariaco Basin sediments have an average δ53Cr value of +0.38 ± 0.10‰ (2σ, n = 7), which shows no dependency on sample location within the basin and is close to that of Atlantic deepwater Cr (∼+0.5‰). This suggests that authigenic Cr in anoxic sediments may reliably reflect the first-order Cr isotope composition of deepwaters. For Peru Margin samples

  8. Isotopic composition of lithium, potassium, rubidium, and strontium in lunar surface material

    NASA Technical Reports Server (NTRS)

    Zaslavskiy, V. G.; Levskiy, L. K.; Murin, A. N.

    1974-01-01

    The isotopic composition of alkali and alkaline earth elements in the Luna 16 regolith was investigated by the method of thermionic emission, without chemical separation. The isotopic composition of the lithium in two regolith samples did not differ (within the limits 0.5 percent) from the mean of the terrestrial reference standard. At the same time, the observed difference (1 percent) in the isotopic composition of lithium between the samples requires further investigation and confirmation. The isotopic compositions of K and Rb did not differ within the limits of experimental error from the isotopic composition of the reference standard.

  9. Groundwater changes in evaporating basins using gypsum crystals' isotopic compositions

    NASA Astrophysics Data System (ADS)

    Gatti, E.; Bustos, D.; Allwood, A.; Coleman, M. L.

    2014-12-01

    While the dynamics of groundwater evaporation are well known, it is still challenging to reconstruct the water patterns in areas where water is not available anymore. We selected a specific location in White Sands National Monument (WSNM), New Mexico, to validate a method to extract information from hydrated minerals regarding past groundwater evaporation patterns in evaporitic basins. WSNM has gypsum (CaSO4.2H2O) dunes and crystals precipitated from the evaporation of an ancient lake. Our approach aims to extract the water of crystallization of gypsum and measure its oxygen and hydrogen isotopic compositions, in order to reconstruct the groundwater history of the area. The idea is that as the mother brine evaporates its isotopic composition changes continuously, recorded as water of crystallization in successive growth zones of gypsum. To check if the isotopic composition of the salt could effectively differentiate between distinctive humidity conditions, the methodology was tested first on synthetic gypsum grown under controlled humidity and temperature conditions. T and RH% were maintained constant in a glove box and precipitated gypsum was harvested every 24 hours. d2H and d18O of water of crystallization from the synthetic gypsum was extracted using a specially developed technique on a TC/EA. The brine was measured using a Gas Bench II for d18O and an H-Device for d2H on a Thermo Finnigan MAT 253 mass spectrometer. With the method tested, we measured natural gypsum. In order to identify the growth zones we mapped the surface of the crystals using an experimental space flight XRF instrument. Crystals were then sampled for isotopic analyses. Preliminary results suggest that site-specific groundwater changes can be described by the isotopic variations. We will show that the methodology is a reliable and fast method to quantify hydrological changes in a targeted environment. The study is currently ongoing but the full dataset will be presented at the conference.

  10. New low-cost dimensionally stable composite linear absolute position encoder scale

    NASA Astrophysics Data System (ADS)

    Hassler, William L., Jr.; Nakayama, Robert K.

    1990-11-01

    A major problem in the use of standard linear position encoders is that the etched glass scales they use have a coefficient of thermal expansion (C. T. E. ) of about 1 1 . Oppm/ C. This means that their position measurements drift with changes in environmental temperature proportional to their C. T. E. . A new low cost dimensionally stable composite scale was made for use in a new absolute linear position encoder. The unidirectional Polyphenylene Sulfide/AS4 carbon fiber composite material that this scale is made of was tested for dimensional stability with respect to changes in temperature humidity and creep. The C. T. E. of the scale material was measured to be nominally 0. 29 ppm/ C with a standard deviation of 0. 12 over the operating temperature range of -2 to 62 C. The overall displacement strain due to 98 moisture absorption relative to 0 moisture absorption was measured to be 9 ppm. The strain due to stress-relief creep was found to be a maximum of 3 ppm over a period of 173 days. These results show that a linear position encoder scale made of this material is superior to those made of the standard glass currently being used and more cost effective than fused silica for most applications. 1.

  11. Nitrogen isotopic composition and density of the Archean atmosphere.

    PubMed

    Marty, Bernard; Zimmermann, Laurent; Pujol, Magali; Burgess, Ray; Philippot, Pascal

    2013-10-04

    Understanding the atmosphere's composition during the Archean eon is fundamental to unraveling ancient environmental conditions. We show from the analysis of nitrogen and argon isotopes in fluid inclusions trapped in 3.0- to 3.5-billion-year-old hydrothermal quartz that the partial pressure of N2 of the Archean atmosphere was lower than 1.1 bar, possibly as low as 0.5 bar, and had a nitrogen isotopic composition comparable to the present-day one. These results imply that dinitrogen did not play a significant role in the thermal budget of the ancient Earth and that the Archean partial pressure of CO2 was probably lower than 0.7 bar.

  12. Oxygen isotopic composition of opaline phytoliths: Potential for terrestrial climatic reconstruction

    SciTech Connect

    Shahack-Gross, R.; Weiner, S.; Shemesh, A.; Yakir, D.

    1996-10-01

    Opaline mineralized bodies are produced by many terrestrial plants and accumulate in certain soils and archaeological sites. Analyses of the oxygen isotopic compositions of these so-called phytoliths from stems and leaves of wheat plants grown in a greenhouse showed a linear relationship with stem and leaf water isotopic compositions and hence, indirectly, rain water isotopic composition. Analyses of wheat plants grown in fields showed that stem phytoliths isotopic composition directly reflects the seasonal air temperature change, whereas leaf phytoliths isotopic composition reflects both temperature and relative humidity. Temperature and the oxygen isotopic composition of stem phytoliths were related by an equation similar to that proposed for marine opal. Oxygen isotopic compositions of fossil phytoliths, and in particular those from stems, could be valuable for reconstructing past terrestrial climate change.

  13. Hydrogen isotopic composition of the water in CR chondrites

    NASA Astrophysics Data System (ADS)

    Bonal, L.; Alexander, C. M. O.'D.; Huss, G. R.; Nagashima, K.; Quirico, E.; Beck, P.

    2013-04-01

    The thermal and aqueous alteration experienced by QUE 99177, MET 00426, EET 92042, GRA 95229, Renazzo and Al Rais CR chondrites was assessed through multi-technique characterization of their the carbonaceous matter and hydrated mineral phases. Each of the chondrites escaped long duration thermal metamorphism as reflected by the low structural order of the polyaromatic carbonaceous matter assessed by Raman spectroscopy. The infrared spectra of the matrix grains clearly reveal the presence of hydrated minerals in each of the CR chondrites. In particular, the extent of aqueous alteration experienced by QUE 99177 and MET 00426 may have been previously underestimated. The H isotopic compositions of the altering fluids were measured in situ in fine-grained phyllosilicates and individual coarse-grained hydrated silicates. In the analyzed CR chondrites, the main observations are that (i) the water is systematically enriched in D, and the enrichments (δDwater up to 1600‰) can be even higher than the highest D-enrichments reported for cometary water; (ii) the isotopic composition of the water is highly variable at the micrometer scale; (iii) there is no clear trend observed in the isotopic composition of the water (maximum D-enrichment, range of variation) along the aqueous alteration sequence. The D-enrichments and spatial variability are easier to explain as secondary signatures acquired through parent body processes, rather than as being due to the accretion of at least two ices with distinct isotopic compositions and sources that did not fully mix when they melted at the start of the aqueous alteration process.

  14. Isotopic composition of precipitation during different atmospheric circulation patterns

    NASA Astrophysics Data System (ADS)

    Brenčič, Mihael; Kononova, Nina; Vreča, Polona

    2016-04-01

    Precipitation generating processes depend on atmospheric circulation patterns and consequently it is expected that its water stable isotopic composition of hydrogen and oxygen is related to them. Precipitation generated at similar atmospheric circulation patterns should have similar empirical distribution of δ2H and δ18O values. There are several approaches in which atmospheric circulation patterns are classified as elementary air circulation mechanisms - ECM; in our approach we have applied Dzerdzeevskii classification. Two types of models of relation between ECM and isotopic composition of precipitation are proposed; first is based on the linear combination of δ2H and δ18O values with precipitation amount weighted average (Brenčič et al., 2015) and the second new one is based on the multiple regression approach. Both approaches make possible also to estimate empirical distributions' dispersion parameters. Application of the models is illustrated on the precipitation records from Ljubljana and Portorož GNIP stations, Slovenia. Estimated values of the parameters for empirical distributions of δ2H and δ18O of each ECM subtype have shown that calculated estimates are reasonable. Brenčič, M., Kononova, N.K., Vreča, P., 2015: Relation between isotopic composition of precipitation and atmospheric circulation patterns. Journal of Hydrology 529, 1422-1432: doi: 10.1016/j.jhydrol.2015.08.040

  15. Alkali elemental and potassium isotopic compositions of Semarkona chondrules

    USGS Publications Warehouse

    Alexander, C.M. O'D.; Grossman, J.N.

    2005-01-01

    We report measurements of K isotope ratios in 28 Semarkona chondrules with a wide range of petrologic types and bulk compositions as well as the compositions of CPX-mesostasis pairs in 17 type I Semarkona chondrules, including two chondrules with radial alkali zonation and 19 type II chondrules. Despite the wide range in K/Al ratios, no systematic variations in K isotopic compositions were found. Semarkona chondrules do not record a simple history of Rayleigh-type loss of K. Experimentally determined evaporation rates suggest that considerable alkali evaporation would have occurred during chondrule formation. Nevertheless, based on Na CPX-mesostasis distribution coefficients, the alkali contents of the cores of most chondrules in Semarkona were probably established at the time of final crystallization. However, Na CPX-mesostasis distribution coefficients also show that alkali zonation in type I Semarkona chondrules was produced by entry of alkalis after solidification, probably during parent body alteration. This alkali metasomatism may have gone to completion in some chondrules. Our preferred explanation for the lack of systematic isotopic enrichments, even in alkali depleted type I chondrule cores, is that they exchanged with the ambient gas as they cooled. ?? The Meteoritical Society, 2005.

  16. The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials

    NASA Technical Reports Server (NTRS)

    Lauretta, D. S.

    2004-01-01

    During the past three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. As part of my startup package I received funds to construct a state-of-the-art experimental facility to study gas-solid reaction kinetics. Much of our effort was spent developing the methodology to measure the abundance and isotopic composition of Hg at ultratrace levels in solid materials. In our first study, the abundance and isotopic composition of Hg was determined in bulk samples of the Murchison (CM) and Allende (CV) carbonaceous chondrites. We have continued our study of mercury in primitive meteorites and expanded the suite of meteorites to include other members of the CM and CV chondrite group as well as CI and CO chondrites. Samples of the CI chondrite Orgueil, the CM chondrites Murray, Nogoya, and Cold Bokkeveld, the CO chondrites Kainsaz, Omans, and Isna, and the CV chondrites Vigarano, Mokoia, and Grosnaja were tested. We have developed a thermal analysis ICP-MS technique and applied it to the study of a suite of thermally labile elements (Zn, As, Se, Cd, In, Sn, Sb, Te, Hg, Au, Tl, Pb, and Bi) in geologic materials as well.

  17. On the Effect of Planetary Stable Isotope Compositions on Growth and Survival of Terrestrial Organisms

    PubMed Central

    Xie, Xueshu; Zubarev, Roman A.

    2017-01-01

    Isotopic compositions of reactants affect the rates of chemical and biochemical reactions. Usually it is assumed that heavy stable isotope enrichment leads to progressively slower reactions. Yet the effect of stable isotopes may be nonlinear, as exemplified by the “isotopic resonance” phenomenon. Since the isotopic compositions of other planets of Solar system, including Mars and Venus, are markedly different from terrestrial (e.g., deuterium content is ≈5 and ≈100 times higher, respectively), it is far from certain that terrestrial life will thrive in these isotopic conditions. Here we found that Martian deuterium content negatively affected survival of shrimp in semi-closed biosphere on a year-long time scale. Moreover, the bacterium Escherichia coli grows slower at Martian isotopic compositions and even slower at Venus’s compositions. Thus, the biological impact of varying stable isotope compositions needs to be taken into account when planning interplanetary missions. PMID:28052100

  18. Magnesium stable isotope composition of Earth's upper mantle

    NASA Astrophysics Data System (ADS)

    Handler, Monica R.; Baker, Joel A.; Schiller, Martin; Bennett, Vickie C.; Yaxley, Gregory M.

    2009-05-01

    The mantle is Earth's largest reservoir of Mg containing > 99% of Earth's Mg inventory. However, no consensus exists on the stable Mg isotope composition of the Earth's mantle or how variable it is and, in particular, whether the mantle has the same stable Mg isotope composition as chondrite meteorites. We have determined the Mg isotope composition of olivine from 22 mantle peridotites from eastern Australia, west Antarctica, Jordan, Yemen and southwest Greenland by pseudo-high-resolution MC-ICP-MS on Mg purified to > 99%. The samples include fertile lherzolites, depleted harzburgites and dunites, cryptically metasomatised ('dry') peridotites and modally metasomatised apatite ± amphibole-bearing harzburgites and wehrlites. Olivine from these samples of early Archaean through to Permian lithospheric mantle have δ25Mg DSM-3 = - 0.22 to - 0.08‰. These data indicate the bulk upper mantle as represented by peridotite olivine is homogeneous within current analytical uncertainties (external reproducibility ≤ ± 0.07‰ [2 sd]). We find no systematic δ25Mg variations with location, lithospheric age, peridotite fertility, or degree or nature of mantle metasomatism. Although pyroxene may have slightly heavier δ25Mg than coexisting olivine, any fractionation between mantle pyroxene and olivine is also within current analytical uncertainties with a mean Δ25Mg pyr-ol = +0.06 ± 0.10‰ (2 sd; n = 5). Our average mantle olivine δ25Mg DSM-3 = - 0.14 ± 0.07‰ and δ26Mg DSM-3 = - 0.27 ± 0.14‰ (2 sd) are indistinguishable from the average of data previously reported for terrestrial basalts, confirming that basalts have stable Mg isotope compositions representative of the mantle. Olivine from five pallasite meteorites have δ25Mg DSM-3 = - 0.16 to - 0.11‰ that are identical to terrestrial olivine and indistinguishable from the average δ25Mg previously reported for chondrites. These data provide no evidence for measurable heterogeneity in the stable Mg isotope

  19. Light and heavy element isotopic compositions of mainstream SiC grains.

    SciTech Connect

    Amari, S.; Clayton, R. N.; Davis, A. M.; Lewis, R. S.; Pellin, M. J.

    1999-02-03

    Although a variety of types of pre-solar SiC grains have been classified by their C, N, and Si isotopic composition, the majority of such grains are so-called mainstream grains and are believed to have come from asymptotic giant branch stars [1]. We have previously reported the Mo isotopic compositions of presolar SiC grains whose C, N, and Si isotopic compositions were not known [2]. Since most presolar SiC grains fall in the mainstream group, we assumed that these grains were mainstream. The excellent match of the Mo isotopic data with expectations for nucleosynthesis in AGB stars was consistent with this identification. In order to better understand the distribution of isotopic compositions in presolar grains, we have begun to measure heavy element isotopic compositions of presolar SiC grains of known C, N and Si isotopic composition.

  20. The triple isotopic composition of oxygen in leaf water

    NASA Astrophysics Data System (ADS)

    Landais, A.; Barkan, E.; Yakir, D.; Luz, B.

    2006-08-01

    The isotopic composition of atmospheric O 2 depends on the rates of oxygen cycling in photosynthesis, respiration, photochemical reactions in the stratosphere and on δ17O and δ18O of ocean and leaf water. While most of the factors affecting δ17O and δ18O of air O 2 have been studied extensively in recent years, δ17O of leaf water—the substrate for all terrestrial photosynthesis—remained unknown. In order to understand the isotopic composition of atmospheric O 2 at present and in fossil air in ice cores, we studied leaf water in field experiments in Israel and in a European survey. We measured the difference in δ17O and δ18O between stem and leaf water, which is the result of isotope enrichment during transpiration. We calculated the slopes of the lines linking the isotopic compositions of stem and leaf water. The obtained slopes in ln( δ17O + 1) vs. ln( δ18O + 1) plots are characterized by very high precision (˜0.001) despite of relatively large differences between duplicates in both δ17O and δ18O (0.02-0.05‰). This is so because the errors in δ18O and δ17O are mass-dependent. The slope of the leaf transpiration process varied between 0.5111 ± 0.0013 and 0.5204 ± 0.0005, which is considerably smaller than the slope linking liquid water and vapor at equilibrium (0.529). We further found that the slope of the transpiration process decreases with atmospheric relative humidity ( h) as 0.522-0.008 × h, for h in the range 0.3-1. This slope is neither influenced by the plant species, nor by the environmental conditions where plants grow nor does it show strong variations along long leaves.

  1. BOREAS TE-5 CO2 Concentration and Stable Isotope Composition

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry

    2000-01-01

    The BOREAS TE-5 team collected measurements in the NSA and SSA on gas exchange, gas composition, and tree growth. This data set contains measurements of the concentration and stable carbon (C-13/C-12 and oxygen (O-18/O-16) isotope ratios of atmospheric CO2 in air samples collected at different heights within forest canopies. The data were collected to determine the influence of photosynthesis and respiration by the forest ecosystems on the concentration and stable isotope ratio of atmospheric CO2 These measurements were collected at the SSA during each 1994 IFC at OJP, OBS, and OA sites. Measurements were also collected at the NSA during each 1994 IFC at the OJP, T6R5S TE UBS, and T2Q6A TE OA sites. The stable isotope ratios are expressed using standard delta notation and in units of per mil. The isotope ratios are expressed relative to the international standard, PDB, for both carbon and oxygen samples. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

  2. The continental shelf benthic iron flux and its isotope composition

    NASA Astrophysics Data System (ADS)

    Severmann, Silke; McManus, James; Berelson, William M.; Hammond, Douglas E.

    2010-07-01

    Benthic iron fluxes from sites along the Oregon-California continental shelf determined using in situ benthic chambers, range from less than 10 μmol m -2 d -1 to values in excess of ˜300 μmol m -2 d -1. These fluxes are generally greater than previously published iron fluxes for continental shelves contiguous with the open ocean (as opposed to marginal seas, bays, or estuaries) with the highest fluxes measured in the regions around the high-sediment discharge Eel River and the Umpqua River. These benthic iron fluxes do not covary with organic carbon oxidation rates in any systematic fashion, but rather seem to respond to variations in bottom water oxygen and benthic oxygen demand. We hypothesize that the highest rates of benthic iron efflux are driven, in part, by the greater availability of reactive iron deposited along these river systems as compared to other more typical continental margin settings. Bioirrigation likely plays an important role in the benthic Fe flux in these systems as well. However, the influence of bottom water oxygen concentrations on the iron flux is significant, and there appears to be a threshold in dissolved oxygen (˜60-80 μM), below which sediment-ocean iron exchange is enhanced. The isotope composition of this shelf-derived benthic iron is enriched in the lighter isotopes, and appears to change by ˜3‰ (δ 56Fe) during the course of a benthic chamber experiment with a mean isotope composition of -2.7 ± 1.1‰ (2 SD, n = 9) by the end of the experiment. This average value is slightly heavier than those from two high benthic Fe flux restricted basins from the California Borderland region where δ 56Fe is -3.4 ± 0.4‰ (2 SD, n = 3). These light iron isotope compositions support previous ideas, based on sediment porewater analyses, suggesting that sedimentary iron reduction fractionates iron isotopes and produces an isotopically light iron pool that is transferred to the ocean water column. In sum, our data suggest that

  3. Oxygen isotopic composition of carbon dioxide in the middle atmosphere.

    PubMed

    Liang, Mao-Chang; Blake, Geoffrey A; Lewis, Brenton R; Yung, Yuk L

    2007-01-02

    The isotopic composition of long-lived trace molecules provides a window into atmospheric transport and chemistry. Carbon dioxide is a particularly powerful tracer, because its abundance remains >100 parts per million by volume (ppmv) in the mesosphere. Here, we successfully reproduce the isotopic composition of CO(2) in the middle atmosphere, which has not been previously reported. The mass-independent fractionation of oxygen in CO(2) can be satisfactorily explained by the exchange reaction with O((1)D). In the stratosphere, the major source of O((1)D) is O(3) photolysis. Higher in the mesosphere, we discover that the photolysis of (16)O(17)O and (16)O(18)O by solar Lyman-alpha radiation yields O((1)D) 10-100 times more enriched in (17)O and (18)O than that from ozone photodissociation at lower altitudes. This latter source of heavy O((1)D) has not been considered in atmospheric simulations, yet it may potentially affect the "anomalous" oxygen signature in tropospheric CO(2) that should reflect the gross carbon fluxes between the atmosphere and terrestrial biosphere. Additional laboratory and atmospheric measurements are therefore proposed to test our model and validate the use of CO(2) isotopic fractionation as a tracer of atmospheric chemical and dynamical processes.

  4. Assessing the ability of isotope-enabled General Circulation Models to simulate the variability of Iceland water vapor isotopic composition

    NASA Astrophysics Data System (ADS)

    Erla Sveinbjornsdottir, Arny; Steen-Larsen, Hans Christian; Jonsson, Thorsteinn; Ritter, Francois; Riser, Camilla; Messon-Delmotte, Valerie; Bonne, Jean Louis; Dahl-Jensen, Dorthe

    2014-05-01

    During the fall of 2010 we installed an autonomous water vapor spectroscopy laser (Los Gatos Research analyzer) in a lighthouse on the Southwest coast of Iceland (63.83°N, 21.47°W). Despite initial significant problems with volcanic ash, high wind, and attack of sea gulls, the system has been continuously operational since the end of 2011 with limited down time. The system automatically performs calibration every 2 hours, which results in high accuracy and precision allowing for analysis of the second order parameter, d-excess, in the water vapor. We find a strong linear relationship between d-excess and local relative humidity (RH) when normalized to SST. The observed slope of approximately -45 o/oo/% is similar to theoretical predictions by Merlivat and Jouzel [1979] for smooth surface, but the calculated intercept is significant lower than predicted. Despite this good linear agreement with theoretical calculations, mismatches arise between the simulated seasonal cycle of water vapour isotopic composition using LMDZiso GCM nudged to large-scale winds from atmospheric analyses, and our data. The GCM is not able to capture seasonal variations in local RH, nor seasonal variations in d-excess. Based on daily data, the performance of LMDZiso to resolve day-to-day variability is measured based on the strength of the correlation coefficient between observations and model outputs. This correlation coefficient reaches ~0.8 for surface absolute humidity, but decreases to ~0.6 for δD and ~0.45 d-excess. Moreover, the magnitude of day-to-day humidity variations is also underestimated by LMDZiso, which can explain the underestimated magnitude of isotopic depletion. Finally, the simulated and observed d-excess vs. RH has similar slopes. We conclude that the under-estimation of d-excess variability may partly arise from the poor performance of the humidity simulations.

  5. On the mean oxygen isotope composition of the Solar System

    NASA Astrophysics Data System (ADS)

    Ozima, M.; Podosek, F. A.; Higuchi, T.; Yin, Q.-Z.; Yamada, A.

    2007-02-01

    Since the first discovery of extraordinary oxygen isotope compositions in carbonaceous meteorites by Clayton et al. [Clayton, R.N., Grossman, L., Mayeda, T.K., 1973. Science 182, 485-488], numerous studies have been done to explain the unusual mass-independent isotope fractionation, but the problem is still unresolved to this day. Clayton's latest interpretation [Clayton, R.N., 2002. Nature 415, 860-861] sheds new light on the problem, and possible hypotheses now seem to be fairly well defined. A key issue is to resolve whether the oxygen isotopes in the Solar System represented by the Sun (solar oxygen) are the same as oxygen isotopes in planetary objects such as bulk meteorites, Mars, Earth, and Moon, or whether the solar oxygen is more similar to the lightest oxygen isotopes observed in CAIs (Calcium Aluminum-rich Inclusions) in primitive meteorites. Here, we examined the problem using oxygen isotope analytical data of about 400 bulk meteorite samples of various classes or types (data compiled by K. Lodders). We used in our discussion exclusively the parameter Δ 17O, a direct measure of the degree of mass-independent isotope fractionation of oxygen isotopes. When Δ 17O is arranged according to a characteristic size of their host planetary object, it shows a systematic trend: (1) Δ 17O values scatter around zero; (2) the scatter from the mean (Δ 17O=0) decreases with increasing representative size of the respective host planetary object. This systematic trend is easily understood on the basis of a hierarchical scenario of planetary formation, that is, larger planetary objects have formed by progressive accretion of planetesimals by random sampling over a wide spectrum of proto-solar materials. If this progressive random sampling of planetesimals were the essential process of planetary formation, the isotopic composition of planetary oxygen should approach that of the solar oxygen. To test this random sampling hypothesis, we applied a multiscale, multistep

  6. Isotopic composition of strontium in sea water throughout Phanerozoic time

    USGS Publications Warehouse

    Peterman, Z.E.; Hedge, C.E.; Tourtelot, H.A.

    1970-01-01

    Isotopic analyses of strontium in primary fossil carbonate reveal significant variations in Sr87 Sr86 of sea water during the Phanerozoic. The strontium isotopic composition may have been uniform from the Ordovician through the Mississippian, with an average Sr87 Sr86 of 0.7078. A subsequent decrease in this value into the Mesozoic is interrupted by two provisionally documented positive pulses in Sr87 Sr86-one in the Early Pennsylvanian and one in the Early Triassic. The lowest observed value (0.7068) occurred in Late Jurassic time, and this was followed by a gradual increase to 0.7075 in the Late Cretaceous and a more rapid increase through the Tertiary to 0.7090 for modern sea water. These variations are thought to be the result of a complex interplay of periods of intense volcanism and epeirogenic movements of the continents on a worldwide scale. ?? 1970.

  7. Differences in isotopic composition of carbonaceous components in enstatite chondrites

    NASA Astrophysics Data System (ADS)

    Grady, M. M.; Wright, I. P.; Carr, R. H.; Poths, J.; Pillinger, C. T.

    1988-02-01

    Carbon stable isotopic composition of the major carbonaceous component in enstatite chondrites varies with petrologic type. Investigation of a suite of HF/HCl-resistant residues has shown that this variation is due to an inherent difference in delta(C-13) of the carbon, and is not a result of the presence of small amounts of isotopically anomalous carbon-bearing components. These latter do occur in type EH3 and EH4 chondrites, in concentrations similar to those found in C1 and C2 carbonaceous chondrites. Combustion of the major carbon component (apparently elemental carbon, not necessarily graphite) occurs at relatively higher temperatures in enstatite chondrites of increasing petrologic type. This is considered to reflect an increase in crystallinity or ordering of the carbonaceous component, and is a measure of the degree of thermal processing to which the meteorites have been subjected during accretion and/or metamorphism.

  8. Tellurium isotope compositions of calcium-aluminum-rich inclusions

    NASA Astrophysics Data System (ADS)

    Fehr, M. A.; Rehkämper, M.; Halliday, A. N.; Hattendorf, B.; Günther, D.

    2009-08-01

    A method for the precise and accurate determination of the tellurium (Te) isotope compositions of calcium-aluminum-rich inclusions (CAIs) has been developed. The technique utilizes multiple-collector inductively coupled plasma-mass spectrometry (MC-ICPMS) with either Faraday detectors or a dual ion-counting system. The external reproducibility (2σ) for 126Te/125Te was ~15‰ and ~2‰ when 3 pg and 65 pg of Te were analyzed with the electron multipliers. Measurements performed on 200 pg of Te using Faraday detectors and time-resolved software displayed an external reproducibility of ~8‰ for 126Te/124Te, whereas 3 ng Te could be measured to a precision of about 0.6‰. Analyses of five CAIs from the Allende chondrite yielded Te concentrations that range from 12 to 537 ppb and the inclusions are therefore depleted in Te relative to bulk Allende by factors of about 2 to 86. The Sn/Te ratios of the CAIs are also fractionated compared to bulk Allende (which displays 124Sn/128Te ≍ 0.1) with 124Sn/128Te ratios of about 0.1 to 2.5. The Te isotope measurements for these refractory inclusions yielded no 126Te excesses from the decay of the short-lived radionuclide 126Sn (τ½ = 234,500 years) and the most precise analysis provided a ɛ126Te value of 1 ± 6 (ɛ126Te = 126Te/ 124Te normalized to 122Te/124Te = 0.53594 and reported relative to the JMC Te standard). Minor differences in the Te isotope composition of the CAIs relative to the terrestrial standard and bulk Allende hint at the presence of small deficits in r-process Te isotopes or excess of s-process Te, but these nucleosynthetic anomalies are barely resolvable given the analytical uncertainties. Hence, it is also conceivable that these effects reflect small unresolved analytical artifacts.

  9. Potential Skin Regeneration Activity and Chemical Composition of Absolute from Pueraria thunbergiana Flower.

    PubMed

    Kim, Do-Yoon; Won, Kyung-Jong; Hwang, Dae-Il; Yoon, Seok Won; Lee, Su Jin; Park, Joo-Hoon; Yoon, Myeong Sik; Kim, Bokyung; Lee, Hwan Myung

    2015-11-01

    The flower of Pueraria thunbergiana BENTH (PTBF) contains isoflavonoids and essential oil components. It has many biological and pharmacological activities, including anti-diabetes, anti-oxidant, and weight loss. However, its effect on skin regeneration remains unknown. In the present study, we isolated the absolute from PTBF through solvent extraction and determined the role of the absolute on skin regeneration-associated responses in human epidermal-keratinocytes (HaCats). The PTBF absolute, which contained 10 compounds, stimulated migration and proliferation and increased the phosphorylation of serine/threonine-specific protein kinase and extracellular signal-regulated kinasel/2 in HaCats. It induced type I and IV collagen synthesis in HaCats. In addition, treatment with PTBF absolute resulted in increased sprout outgrowth in HaCats. These findings suggest that PTBF absolute may participate in skin regeneration, probably through promotion of migration, proliferation, and collagen synthesis.

  10. Isotopic composition of zinc, copper, and iron in lunar samples

    NASA Astrophysics Data System (ADS)

    Moynier, F.; Albarède, F.; Herzog, G. F.

    2006-12-01

    We determined by ICP-MS the concentrations and isotopic ratios of Fe, Cu, and Zn in the Ti-rich lunar basalt 74275, in the lunar orange glass 74220, and in up to 10 lunar soils, namely, 14163, 15231, 64501, 66041, 68841, 69941, 70011, 72501, 75081, and 76501. Two analyses of zinc in lunar basalt 74275 give δ 66Zn = 0.17‰ and 0.75‰, values within the range of those measured in terrestrial basalts; copper in lunar basalt 74275 has δ 65Cu ˜ +1.4‰, which is isotopically heavier than values observed in terrestrial basalts. In the orange glass, we measured δ 56Fe = -0.24‰, δ 65Cu = -0.42‰, and δ 66Zn ˜ -3.6‰. These values of δ are more negative than those obtained for 74275 and for typical lunar basalts, but for Cu, comparable to those observed in terrestrial sulfides and meteorites. In lunar soils we found 0.11‰ ⩽ δ 56Fe ⩽ 0.51‰, 2.6‰ ⩽ δ 65Cu ⩽ 4.5‰, and 2.2‰ ⩽ δ 66Zn ⩽ 6.4‰. Insofar as we can generalize from a small sample set, S, Fe, Cu, Zn, and Cd show similar trends in isotopic fractionation on the Moon. Lunar basalts have nearly terrestrial isotopic ratios. Relative to the lunar basalt 74275, the pyroclastic glass 74220 is enriched in the lighter isotopes of Fe, Cu, and Zn, and the soils are enriched in the heavier isotopes of Fe, Cu, and Zn. The patterns in the basalts are likely inherited from the source material; the light-isotope enrichments seen in the orange glass originated during lava fountaining or, less probably, during partial condensation of vapor; and the heavy-isotope enrichments in the lunar soils were likely created by a combination of processes that included micrometeorite vaporization and sputtering. In the orange glass, the light-isotope enrichments (relative to lunar basalts) of Zn are larger than those of Cu. If these enrichments reflect accurately the isotopic composition of the gas, they suggest that Cu is more volatile than Zn in the liquid from which the gas derived. A simple model built on

  11. Oxygen isotope composition of mafic magmas at Vesuvius

    NASA Astrophysics Data System (ADS)

    Dallai, L.; Cioni, R.; Boschi, C.; D'Oriano, C.

    2009-12-01

    The oxygen isotope composition of olivine and clinopyroxene from four plinian (AD 79 Pompeii, 3960 BP Avellino), subplinian (AD 472 Pollena) and violent strombolian (Middle Age activity) eruptions were measured to constrain the nature and evolution of the primary magmas of the last 4000 years of Mt. Vesuvius activity. A large set of mm-sized crystals was accurately separated from selected juvenile material of the four eruptions. Crystals were analyzed for their major and trace element compositions (EPMA, Laser Ablation ICP-MS), and for 18O/16O ratios. As oxygen isotope composition of uncontaminated mantle rocks on world-wide scale is well constrained (δ18Oolivine = 5.2 ± 0.3; δ18Ocpx = 5.6 ± 0.3 ‰), the measured values can be conveniently used to monitor the effects of assimilation/contamination of crustal rocks in the evolution of the primary magmas. Instead, typically uncontaminated mantle values are hardly recovered in Italian Quaternary magmas, mostly due to the widespread occurrence of crustal contamination of the primary magmas during their ascent to the surface (e.g. Alban Hills, Ernici Mts., and Aeolian Islands). Low δ18O values have been measured in olivine from Pompeii eruption (δ18Oolivine = 5.54 ± 0.03‰), whereas higher O-compositions are recorded in mafic minerals from pumices or scoria of the other three eruptions. Measured olivine and clinopyroxene share quite homogeneous chemical compositions (Olivine Fo 85-90 ; Diopside En 45-48, respectively), and represent phases crystallized in near primary mafic magmas, as also constrained by their trace element compositions. Data on melt inclusions hosted in crystals of these compositions have been largely collected in the past demonstrating that they crystallized from mafic melt, basaltic to tephritic in composition. Published data on volatile content of these melt inclusions reveal the coexistence of dissolved water and carbon dioxide, and a minimum trapping pressure around 200-300 MPa, suggesting

  12. The concentration and isotopic composition of osmium in the oceans

    SciTech Connect

    Sharma, M.; Papanastassiou, D.A.; Wasserburg, G.J.

    1997-08-01

    Osmium is one of the rarer elements in seawater. Analytical difficulties have previously prevented the direct measurement of the osmium concentration and isotopic composition in seawater. We report a chemical separation procedure that yields quantitative extraction of osmium standard and of osmium tracer by iron hydroxide precipitation from seawater doped with osmium standard, osmium tracer, and FeCl{sub 3}. The iron hydroxide precipitate is processed to extract osmium, using techniques developed for iron meteorites. Utilizing this procedure, water samples from the Pacific and Atlantic oceans were analyzed for osmium concentration and isotopic composition. Direct determination of the osmium concentration of seawater gives between 15 and 19 fM kg{sup -1}. Detailed experiments on different aliquots of one seawater sample from the North Atlantic Ocean, keeping the amounts of reagents constant, yield concentrations from 16 to 19 fM kg{sup -1}. The variability in concentration is outside the uncertainty introduced because of blanks and indicates a lack of full equilibration between the osmium tracer and seawater osmium. The most reliable osmium concentration of the North Atlantic deep ocean water is 19 fM kg {sup -1} with the {sup 187}Os/{sup 186}Os ratio being 8.7{+-}2 (2{sigma}). Detailed experiments on one seawater sample from the Central Pacific Ocean indicate that the most reliable osmium concentration of the deep ocean water from the Central Pacific is 19 fM kg{sup -1} with the {sup 187}Os/{sup 186}Os ratio being 8.7{+-}0.3 (2{sigma}). The directly measured osmium isotopic composition of the oceans is in good agreement with that obtained from the analysis of some rapidly accumulating organic rich sediments. A sample of ambient seawater around the Juan de Fuca Ridge gave {sup 187}Os/{sup 186}Os = 6.9{+-} 0.4. 42 refs., 6 figs., 4 tabs.

  13. Mass-independent sulfur isotopic compositions in stratospheric volcanic eruptions.

    PubMed

    Baroni, Mélanie; Thiemens, Mark H; Delmas, Robert J; Savarino, Joël

    2007-01-05

    The observed mass-independent sulfur isotopic composition (Delta33S) of volcanic sulfate from the Agung (March 1963) and Pinatubo (June 1991) eruptions recorded in the Antarctic snow provides a mechanism for documenting stratospheric events. The sign of Delta33S changes over time from an initial positive component to a negative value. Delta33S is created during photochemical oxidation of sulfur dioxide to sulfuric acid on a monthly time scale, which indicates a fast process. The reproducibility of the results reveals that Delta33S is a reliable tracer to chemically identify atmospheric processes involved during stratospheric volcanism.

  14. The carbon isotopic composition of Novo Urei diamonds

    NASA Technical Reports Server (NTRS)

    Fisenko, A. V.; Semjenova, L. F.; Verchovsky, A. B.; Russell, S. S.; Pillinger, C. T.

    1993-01-01

    The carbon isotopic composition of diamond grains isolated from the Novo Urei meteorite are discussed. A diamond separate was obtained from 2g of whole rock using the chemical treatments described aimed at obtaining very pure diamond. X ray diffraction of the residue, which represented 5000 ppm of the parent mass, indicated only the presence of the desired mineral. The diamond crystals were 1-30 microns in diameter, and some grains had a yellow color. The chemical treatments were followed by a size separation to give a 1-10 microns and a 5-30 microns fraction, which were named DNU-1 and DNU-2, respectively.

  15. Novel isotopic N, N-Dimethyl Leucine (iDiLeu) Reagents Enable Absolute Quantification of Peptides and Proteins Using a Standard Curve Approach

    NASA Astrophysics Data System (ADS)

    Greer, Tyler; Lietz, Christopher B.; Xiang, Feng; Li, Lingjun

    2015-01-01

    Absolute quantification of protein targets using liquid chromatography-mass spectrometry (LC-MS) is a key component of candidate biomarker validation. One popular method combines multiple reaction monitoring (MRM) using a triple quadrupole instrument with stable isotope-labeled standards (SIS) for absolute quantification (AQUA). LC-MRM AQUA assays are sensitive and specific, but they are also expensive because of the cost of synthesizing stable isotope peptide standards. While the chemical modification approach using mass differential tags for relative and absolute quantification (mTRAQ) represents a more economical approach when quantifying large numbers of peptides, these reagents are costly and still suffer from lower throughput because only two concentration values per peptide can be obtained in a single LC-MS run. Here, we have developed and applied a set of five novel mass difference reagents, isotopic N, N-dimethyl leucine (iDiLeu). These labels contain an amine reactive group, triazine ester, are cost effective because of their synthetic simplicity, and have increased throughput compared with previous LC-MS quantification methods by allowing construction of a four-point standard curve in one run. iDiLeu-labeled peptides show remarkably similar retention time shifts, slightly lower energy thresholds for higher-energy collisional dissociation (HCD) fragmentation, and high quantification accuracy for trypsin-digested protein samples (median errors <15%). By spiking in an iDiLeu-labeled neuropeptide, allatostatin, into mouse urine matrix, two quantification methods are validated. The first uses one labeled peptide as an internal standard to normalize labeled peptide peak areas across runs (<19% error), whereas the second enables standard curve creation and analyte quantification in one run (<8% error).

  16. Tracing mercury contamination sources in sediments using mercury isotope compositions.

    PubMed

    Feng, Xinbin; Foucher, Delphine; Hintelmann, Holger; Yan, Haiyu; He, Tianrong; Qiu, Guangle

    2010-05-01

    Mercury (Hg) isotope ratios were determined in two sediment cores collected from two adjacent reservoirs in Guizhou, China, including Hongfeng Reservoir and Baihua Reservoir. Hg isotope compositions were also analyzed in a soil sample collected from the catchment of Hongfeng Reservoir and three cinnabar samples collected from the Wanshan Hg mine. Baihua Reservoir was contaminated with runoff from Guizhou Organic Chemical Plant (GOCP) when metallic Hg was used as a catalyst to produce acetic acid. Hongfeng Reservoir, located upstream of Baihua, receives Hg from runoff and atmospheric deposition. We demonstrated that delta(202)Hg values relative to NIST 3133 of sediment in Baihua Reservoir ranging from -0.60 to -1.10 per thousand were distinctively different from those in Hongfeng Reservoir varying from -1.67 to -2.02 per thousand. While sediments from both Baihua and Hongfeng Reservoirs were characterized by mass dependent variation (MDF), only Hongfeng Reservoir sediments were characterized by mass independent variation (MIF). Moreover, by using a binary mixing model, we demonstrated the major source of Hg in sediment of Hongfeng Reservoir was from runoff due to soil erosion, which was consistent with the conclusion obtained from a previous Hg balance study. This study demonstrates Hg isotope data are valuable tracers for determining Hg contamination sources in sediments.

  17. On the isotopic composition of magmatic carbon in SNC meteorites

    NASA Technical Reports Server (NTRS)

    Wright, I. P.; Grady, M. M.; Pillinger, C. T.

    1992-01-01

    SNC meteorites are thought, from many lines of evidence, to come from Mars. A line of investigation which has been pursued in our laboratory over the years involves measurement of the stable isotopic composition of carbon, in its various forms, in SNC meteorites. In order to establish a firm basis for studying the isotopic systematics of carbon in the martian surface environment, it is first necessary to try and constrain the delta C-13 of bulk Mars. Taking all of the available information, it would seem that the delta C-13 of the Earth's mantle lies somewhere in the range of -5 to -7 percent. Preliminary assessment of magnetic carbon in SNC meteorites, would tend to suggest a delta C-13 of 20 to 30 percent, which is conspicuously different from that of the terrestrial mantle. It is not obvious why there should be such a difference between the two planets, although many explanations are possible. One of these possibilities, that previous delta C-13 measurements for magnetic carbon in SNC meteorites are in error to some degree, is being actively investigated. The most recent results seem to constrain the theta C-13 of the magnetic carbon in SNC meteorites to about -20 percent, which is not at odds with previous estimates. As such, it is considered that a detailed investigation of the carbon isotopic systematics of martian surface materials does have the necessary information with which to proceed.

  18. Mercury emissions and stable isotopic compositions at Vulcano Island (Italy)

    NASA Astrophysics Data System (ADS)

    Zambardi, T.; Sonke, J. E.; Toutain, J. P.; Sortino, F.; Shinohara, H.

    2009-01-01

    Sampling and analyses methods for determining the stable isotopic compositions of Hg in an active volcanic system were tested and optimized at the volcanic complex of Vulcano (Aeolian Islands, Italy). Condensed gaseous fumarole Hg (fum)T, plume gaseous elemental Hg (g)0 and plume particulate Hg (p)II were obtained at fumaroles F0, F5, F11, and FA. The average total Hg emissions, based on Hg T/SO 2 in condensed fumarolic gases and plumes, range from 2.5 to 10.1 kg y - 1 , in agreement with published values [Ferrara, R., Mazzolai, B., Lanzillotta, E., Nucaro, E., Pirrone, N., 2000. Volcanoes as emission sources of atmospheric mercury in the Mediterranean Basin. Sci. Total Environ. 259(1-3), 115-121; Aiuppa, A., Bagnato, E., Witt, M.L.I., Mather, T.A., Parello, F., Pyle, D.M., Martin, R.S., 2007. Real-time simultaneous detection of volcanic Hg and SO 2 at La Fossa Crater, Vulcano (Aeolian Islands, Sicily). Geophys. Res. Lett. 34(L21307).]. Plume Hg (p)II increases with distance from the fumarole vent, at the expense of Hg (g)0 and indicates significant in-plume oxidation and condensation of fumarole Hg (fum)T. Relative to the NIST SRM 3133 Hg standard, the stable isotopic compositions of Hg are δ 202Hg (fum)T = - 0.74‰ ± 0.18 (2SD, n = 4) for condensed gaseous fumarole Hg (fum)T, δ 202Hg (g)0 = - 1.74‰ ± 0.36 (2SD, n = 1) for plume gaseous elemental Hg (g)0 at the F0 fumarole, and δ 202Hg (p)II = - 0.11‰ ± 0.18 (2SD, n = 4) for plume particulate Hg (p)II. The enrichment of Hg (p)II in the heavy isotopes and Hg (g)0 in the light isotopes relative to the total condensed fumarolic Hg (fum)T gas complements the speciation data and demonstrates a gas-particle fractionation occurring after the gas expulsion in ambient T° atmosphere. A first order Rayleigh equilibrium condensation isotope fractionation model yields a fractionation factor α cond-gas of 1.00135 ± 0.00058.

  19. Determination of triple oxygen isotopic compositions of nitrate by using continuous-flow isotope ratio MS.

    NASA Astrophysics Data System (ADS)

    Komatsu, D. D.; Ohkubo, S.; Ishimura, T.; Nakagawa, F.; Tsunogai, U.

    2006-12-01

    The triple oxygen isotopic compositions (18O/16O and 17O/16O) of nitrate in natural waters can be a useful tracer to clarify the sources. The triple oxygen isotopic compositions of nitrate have been usually determined by using conventional IRMS system using O2 molecule converted from nitrate through multiple reaction/purification steps. The traditional methods, however, required at least 1-100 μmol quantities of nitrate so that applications of the methods to various environmental nitrate samples were difficult. Thus, we developed a rapid and sensitive analytical system to determine the triple oxygen isotopic compositions of nitrate in nmol quantities using continuous-flow IRMS (CF-IRMS) without the cumbersome and time-consuming pretreatments. Our method is based on the isotopic analysis of N2O quantitatively converted from nitrate based on the simple reactions using spongy cadmium and sodium azide in an acetic acid buffer. However, we cannot determine 17O/16O ratio of N2O directly by measuring the masses 44, 45, and 46 of N2O introduced to IRMS, because the measured output of mass 45 from IRMS consists of 14N15N16O, 15N14N16O, and 14N14N17O. Thus, addition to the N2O isotopic analysis at the masses 44, 45, and 46, the 15N/14N ratio is determined separately for the same sample N2O. To attain this purpose, two instrumental approaches were done. In the first system, the N2+ fragment ion beams of N2O at masses 28 and 29 were used to determine the 15N/14N ratio of N2O. While the analytical precisions better than 0.5 ‰ for 20 nmol N2O injections and better than 1.0 ‰ for 7 nmol N2O injections were obtained for 15N/14N ratio, we found that the accuracy strongly depended on the quantities introduced. In the second system, the N2 molecules, converted from N2O using an on line Cu reduction furnace (720 degree) was used to determine the 15N/14N ratio of N2O. The analytical precisions better than 0.1 ‰ for 5 nmol N2O injections and better than 0.4 ‰ for 1 nmol N2O

  20. The isotopic composition of iron-group galactic cosmic rays

    NASA Technical Reports Server (NTRS)

    Wiedenbeck, M. E.; Leske, R. A.

    1995-01-01

    Results from studies of the isotopic composition of iron group elements in the galactic cosmic radiation are reviewed, emphasizing recently reported measurements from the ISEE-3 spacecraft. The observed isotope distributions for the elements Ti through Mn are in good agreement with those expected for a propagated solar-like source composition, with the possible exception of an enhanced abundance of Ti-50. It is found that a significant fraction of the radioactive secondary nuclide Mn-54 has decayed, indicating a confinement time of iron group cosmic rays in the galaxy of at least 2 Myr. The source ratio Fe-54/Fe-56 is found to be consistent with the solar value, but the ratio Ni-60/Ni-58 is greater than solar by a factor of 2.8+/-1.0. The measured abundance of Co-59 is significantly greater than the calculated secondary contribution, suggesting that this nuclide has been produced in the source regions by the electron capture decay of Ni-59 and implying a time delay between nucleosynthesis and acceleration approximately greater than 10(exp 5) yr.

  1. The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials

    NASA Technical Reports Server (NTRS)

    Blum, J. D.; Klaue, Bjorn

    2005-01-01

    During the three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. At the time the grant started, our collaborating PI, Dante Lauretts, was a postdoctoral research associate working with Peter Buseck at Arizona State University. The work on chondritic Hg was done in collaboration with Dante Lauretta and Peter Buseck and this study was published in Lauretta et a1 (2001a). In July, 2001 Dante Lauretta accepted a position as an Assistant Professor in the Lunar and Planetary Laboratory at the University of Arizona. His funding was transferred and this grant has supported much of his research activities during his first two years at the U of A. Several other papers are in preparation and will be published soon. We presented papers on this topic at Goldschmidt Conferences, the Lunar and Planetary Science Conferences, and the Annual Meetings of the Meteoritical Society. The work done under this grant has spurred several new directions of inquiry, which we are still pursuing. Included in this paper are the studies of bulk abundances and isotopic compositions of metreoritic Mercury, and the development of a thermal analysis ICP-MS technique applied to thermally liable elements.

  2. Seasonality of Leaf Carbon Isotopic Composition and Leaf Water Isotopic Enrichment in a Mixed Evergreen Forest in Southern California

    NASA Astrophysics Data System (ADS)

    Santiago, L. S.; Sickman, J. O.; Goulden, M.; DeVan, C.; Pasquini, S. C.; Pivovaroff, A. L.

    2011-12-01

    Leaf carbon isotopic composition and leaf water isotopic enrichment reflect physiological processes and are important for linking local and regional scale processes to global patterns. We investigated how seasonality affects the isotopic composition of bulk leaf carbon, leaf sugar carbon, and leaf water hydrogen under a Mediterranean climate. Leaf and stem samples were collected monthly from four tree species (Calocedrus decurrens, Pinus lambertiana, Pinus ponderosa, and Quercus chrysolepis) at the James San Jacinto Mountain Reserve in southern California. Mean monthly bulk leaf carbon isotopic composition varied from -34.5 % in P. ponderosa to -24.7 % in P. lambertiana and became more depleted in 13C from the spring to the summer. Mean monthly leaf sugar varied from -29.3 % in P. ponderosa to -21.8 % in P. lambertiana and was enriched in 13C during the winter, spring and autumn, but depleted during the mid-summer. Leaf water hydrogen isotopic composition was 28.4 to 68.8 % more enriched in deuterium than source water and this enrichment was greater as seasonal drought progressed. These data indicate that leaf carbon and leaf water hydrogen isotopic composition provide sensitive measures that connect plant physiological processes to short-term climatic variability.

  3. The chlorine isotopic composition of Martian meteorites 1: Chlorine isotope composition of Martian mantle and crustal reservoirs and their interactions

    NASA Astrophysics Data System (ADS)

    Williams, J. T.; Shearer, C. K.; Sharp, Z. D.; Burger, P. V.; McCubbin, F. M.; Santos, A. R.; Agee, C. B.; McKeegan, K. D.

    2016-11-01

    The Martian meteorites record a wide diversity of environments, processes, and ages. Much work has been done to decipher potential mantle sources for Martian magmas and their interactions with crustal and surface environments. Chlorine isotopes provide a unique opportunity to assess interactions between Martian mantle-derived magmas and the crust. We have measured the Cl-isotopic composition of 17 samples that span the range of known ages, Martian environments, and mantle reservoirs. The 37Cl of the Martian mantle, as represented by the olivine-phyric shergottites, NWA 2737 (chassignite), and Shergotty (basaltic shergottite), has a low value of approximately -3.8‰. This value is lower than that of all other planetary bodies measured thus far. The Martian crust, as represented by regolith breccia NWA 7034, is variably enriched in the heavy isotope of Cl. This enrichment is reflective of preferential loss of 35Cl to space. Most basaltic shergottites (less Shergotty), nakhlites, Chassigny, and Allan Hills 84001 lie on a continuum between the Martian mantle and crust. This intermediate range is explained by mechanical mixing through impact, fluid interaction, and assimilation-fractional crystallization.

  4. Continuous measurements of isotopic composition of water vapour on the East Antarctic Plateau

    NASA Astrophysics Data System (ADS)

    Casado, Mathieu; Landais, Amaelle; Masson-Delmotte, Valérie; Genthon, Christophe; Kerstel, Erik; Kassi, Samir; Arnaud, Laurent; Picard, Ghislain; Prie, Frederic; Cattani, Olivier; Steen-Larsen, Hans-Christian; Vignon, Etienne; Cermak, Peter

    2016-07-01

    Water stable isotopes in central Antarctic ice cores are critical to quantify past temperature changes. Accurate temperature reconstructions require one to understand the processes controlling surface snow isotopic composition. Isotopic fractionation processes occurring in the atmosphere and controlling snowfall isotopic composition are well understood theoretically and implemented in atmospheric models. However, post-deposition processes are poorly documented and understood. To quantitatively interpret the isotopic composition of water archived in ice cores, it is thus essential to study the continuum between surface water vapour, precipitation, surface snow and buried snow. Here, we target the isotopic composition of water vapour at Concordia Station, where the oldest EPICA Dome C ice cores have been retrieved. While snowfall and surface snow sampling is routinely performed, accurate measurements of surface water vapour are challenging in such cold and dry conditions. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces. Two infrared spectrometers have been deployed at Concordia, allowing continuous, in situ measurements for 1 month in December 2014-January 2015. Comparison of the results from infrared spectroscopy with laboratory measurements of discrete samples trapped using cryogenic sampling validates the relevance of the method to measure isotopic composition in dry conditions. We observe very large diurnal cycles in isotopic composition well correlated with temperature diurnal cycles. Identification of different behaviours of isotopic composition in the water vapour associated with turbulent or stratified regime indicates a strong impact of meteorological processes in local vapour/snow interaction. Even if the vapour isotopic composition seems to be, at least part of the time, at equilibrium with the local snow, the slope of δD against δ18O prevents us from identifying a unique origin leading

  5. Perchlorate in The Great Lakes: Distribution, Isotopic Composition and Origin

    NASA Astrophysics Data System (ADS)

    Poghosyan, A.; Sturchio, N. C.; Jackson, W. A.; Guan, Y.; Eiler, J. M.; Hatzinger, P. B.

    2013-12-01

    Concentrations, stable chlorine and oxygen isotopic compositions, and 36Cl abundances of perchlorate were investigated in the five Laurentian Great Lakes. Samples were collected during monitoring cruises in 2007 and 2008 of the U.S. EPA's RV Lake Guardian and in 2010 at the water supply intake of Marquette, MI on the southern shore of Lake Superior. Concentrations of perchlorate were measured by IC/MS/MS at 24 locations, including one or two depth profiles in each lake. Mean concentrations (μg/L) are: Superior, 0.06 × 0.01; Michigan, 0.10 × 0.01; Huron, 0.11 × 0.01; Erie, 0.08 × 0.01, and Ontario, 0.09 × 0.01. Concentration vs. depth is nearly constant in each lake, indicating well-mixed conditions. Perchlorate was extracted from near-surface water by passing 15,000 to 80,000 L of water through 1-L cartridges containing Purolite A530E bifunctional anion-exchange resin. In the laboratory, perchlorate was eluted from the resin, purified, and precipitated as a >99% pure crystalline phase. Milligram amounts were recovered from each lake. Chlorine and oxygen isotopic analyses were performed at Caltech using the Cameca 7f-GEO SIMS instrument, following validation of the SIMS method with analyses of USGS-37 and USGS-38 isotopic reference materials. Results indicate a relatively narrow range in δ37Cl values (+2.9 to +3.9 ‰) and a wider range in δ18O values (-4.0 to +4.1 ‰), with a general geographic trend of increasing δ18O from west to east. Oxygen-17 was measured at UIC using dual-inlet IRMS of O2 produced by decomposition of KClO4. Great Lakes perchlorate has mass-independent oxygen isotopic variations with positive Δ17O values (+1.6 ‰ to +2.7 ‰) divided into two distinct groups: Lake Superior (+2.7 ‰) and the other four lakes (~ +1.7 ‰). The isotopic data indicate that perchlorate is dominantly of natural origin, having stable isotopic compositions resembling those of perchlorate from pre-industrial groundwaters in the western USA. The 36Cl

  6. Lithium Isotopic Composition of Mantle Plumes and the Distribution of Lithium Isotopes Among Earth's Reservoirs

    NASA Astrophysics Data System (ADS)

    Chan, L.; Hart, S. R.; Blusztajn, J. S.; Lassiter, J. C.; Frey, F. A.; Hauri, E. H.

    2006-12-01

    We have determined lithium isotopic compositions of seventy nearly unaltered basaltic lavas from the Samoan and Cook-Austral volcanic chains, and Pitcairn Island. In addition, the Li isotope record of Mauna Kea has been extended from 3.1 km to 3.3 km using the newly recovered deep drill core of Hawaii Scientific Drilling Project (HSDP-2). From the results of the Hawaii and South Pacific hotspots, we examine the source components of mantle plumes and consider the distribution of Li isotopes among Earth's major reservoirs. The total δ^{7}Li range observed in South Pacific and Hawaiian islands is 2.5 to 7.5‰, suggesting considerable heterogeneity in the deep mantle. The Hawaiian plume occupies the lower range, 2.5 to 5.7‰. Cook-Austral samples depict mixing between HIMU and depleted mantle (DM) components. The DM endmember has δ^{7}Li values of 3.2 to 4.2‰, identical to MORB. HIMU type lavas are isotopically heavier than MORB, reflecting the influence of recycled oceanic crust. The most extreme HIMU signature was observed at Mangaia (7.4‰; Nishio et al., 2005). The EM1 composition shown by Pitcairn is relatively light (3.3 to 4.1‰) and resembles the global average of subducting sediments (~3‰). Malumalu seamount of the Samoan chain defines the most extreme composition of the EM2 mantle; δ^{7}Li range from 4.5 to 5.6‰. High 3He/4He samples of Ofu Island (R/Ra = 24 to 33.7) suggest that the least degassed mantle has δ^{7}Li of about 3‰. In addition to these classic mantle endmembers, we observe an additional component that elevates Samoan lavas above the typical mantle baseline (~3‰) up to 7.5‰. The source of this enrichment is likely mantle wedge material that has been metasomatized by 7Li-rich slab fluids (Elliott et al., 2004). On the other hand, recent studies suggest that a large portion of subducted Li can be retained in high-pressure metamorphosed slab (Marschall et al., in press). This implies that deeply subducted slab need not be

  7. Evaluating Foraminifera as an Archive for Seawater Chromium Isotopic Composition

    NASA Astrophysics Data System (ADS)

    Wang, X.; Planavsky, N.; Hull, P. M.; Tripati, A.; Reinhard, C.; Zou, H.; Elder, L. E.; Henehan, M. J.

    2015-12-01

    In recent years there has been growing interest in using chromium isotopes (δ53Cr) as a proxy to investigate the redox evolution of Earth's ocean-atmosphere system throughout geological history. Potential archives for seawater δ53Cr that have been identified to date include iron formations and organic-rich siliciclastic sediments. However, these types of sediments are not common and they are discontinuous over geologic time. As a result, alternative types of archives are needed. Here we evaluate the utility of foraminifera tests as a recorder of seawater δ53Cr. Core-tops used were from different ocean basins. Mono-specific samples of Globigerinoides sacculifer, Orbulina universa, Pulleniatina obliquiloculata, Globoratalia crassula-crassaformis, Globoratalia truncatulinoides, and Globigerinella siphonifera were isolated to investigate inter-species isotope fractionation. Chromium concentrations were measured by isotope dilution method to be 0.1-0.3 μg/g. The δ53Cr values of these species range from 0.2‰ to 2.4‰, with an analytical uncertainty of 0.3‰ (95% confidence). Despite the high analytical uncertainty due to the extremely low levels of Cr present, there is still large detectable variation in foraminiferal δ53Cr values, which overlap presently available seawater values (Bonnand et al., 2013; Scheiderich et al., 2015). Possible explanations for such variations in foraminiferal δ53Cr values include heterogeneity of seawater δ53Cr in the modern oceans, and/or photobiochemical redox cycling of Cr in the surface oceans. Therefore, care should be taken when using foraminifera to reconstruct past seawater δ53Cr values. ReferencesBonnand, P., James, R., Parkinson, I., Connelly, D., Fairchild, I., 2013. The chromium isotopic composition of seawater and marine carbonates. Earth and Planetary Science Letters, 382: 10-20. Scheiderich, K., Amini, M., Holmden, C., Francois, R., 2015. Global variability of chromium isotopes in seawater demonstrated by Pacific

  8. Variations in Urine Calcium Isotope: Composition Reflect Changes in Bone Mineral Balance in Humans

    NASA Technical Reports Server (NTRS)

    Skulan, Joseph; Anbar, Ariel; Bullen, Thomas; Puzas, J. Edward; Shackelford, Linda; Smith, Scott M.

    2004-01-01

    Changes in bone mineral balance cause rapid and systematic changes in the calcium isotope composition of human urine. Urine from subjects in a 17 week bed rest study was analyzed for calcium isotopic composition. Comparison of isotopic data with measurements of bone mineral density and metabolic markers of bone metabolism indicates the calcium isotope composition of urine reflects changes in bone mineral balance. Urine calcium isotope composition probably is affected by both bone metabolism and renal processes. Calcium isotope. analysis of urine and other tissues may provide information on bone mineral balance that is in important respects better than that available from other techniques, and illustrates the usefulness of applying geochemical techniques to biomedical problems.

  9. New Oxygen Isotope Measurements of Four Stardust Impact Crater Residues Show IDP-Like Compositions

    NASA Astrophysics Data System (ADS)

    Snead, C. J.; McKeegan, K. D.

    2015-07-01

    We have measured the oxygen isotope compositions of four Stardust impact crater residues. These analyses reveal compositions that are similar to those found in interplanetary dust particles, antarctic micrometeorites and CI chondrite components.

  10. Triple sulfur isotope composition of Late Archean seawater sulfate

    NASA Astrophysics Data System (ADS)

    Paris, G.; Fischer, W. W.; Sessions, A. L.; Adkins, J. F.

    2013-12-01

    Multiple sulfur isotope ratios in Archean sedimentary rocks have provided powerful insights into the behavior of the ancient sulfur cycle, the redox state of fluid Earth, and the timing of the rise of atmospheric oxygen [1]. Most processes fractionate sulfur isotopes in proportion to their mass differences, but the Archean sulfur isotope record is marked by pronounced mass-independent fractionation (MIF, Δ33S≠0). The origin of these signatures has been traditionally interpreted as the result of photolysis of SO2 from short wavelength UV light, with positive Δ33S values recorded in pyrite and negative Δ33S values in sulfate-bearing phases [2]. This long-held hypothesis rests on observations of negative Δ33S from enigmatic barite occurrences from mixed volcanic sedimentary strata in Mesoarchean greenstone terrains. Despite forming the framework for understanding Archean sulfur cycle processes [3], it is largely untested [3]. It is largely untested. Consequently, the biggest challenge to our current understanding of the early sulfur cycle is a poor understanding of the isotopic composition of seawater sulfate. Sulfate evaporite minerals are absent from Archean strata and the sulfur isotope record is written entirely by measurements of pyrite. Carbonate associated sulfate (CAS) provides an important archive for assaying the isotopic composition of ancient seawater sulfate It has been exploited in many studies of Phanerozoic and Proterozoic sulfate but have been only marginally used thus far for Archean samples because of the extremely low concentration of CAS in limestones and dolomites from this era. We have developed a novel MC-ICP-MS approach to solve this problem [4]. This new method lowers the detection limit by up to three orders of magnitude for δ34S and Δ33S measurements, enabling to work on a few nmols of sulfate which represent only tens of mg of sample powders micromilled from specific carbonate textures. Two stratigraphic sections from the 2

  11. Argon isotopic composition of Archaean atmosphere probes early Earth geodynamics.

    PubMed

    Pujol, Magali; Marty, Bernard; Burgess, Ray; Turner, Grenville; Philippot, Pascal

    2013-06-06

    Understanding the growth rate of the continental crust through time is a fundamental issue in Earth sciences. The isotopic signatures of noble gases in the silicate Earth (mantle, crust) and in the atmosphere afford exceptional insight into the evolution through time of these geochemical reservoirs. However, no data for the compositions of these reservoirs exists for the distant past, and temporal exchange rates between Earth's interior and its surface are severely under-constrained owing to a lack of samples preserving the original signature of the atmosphere at the time of their formation. Here, we report the analysis of argon in Archaean (3.5-billion-year-old) hydrothermal quartz. Noble gases are hosted in primary fluid inclusions containing a mixture of Archaean freshwater and hydrothermal fluid. Our analysis reveals Archaean atmospheric argon with a (40)Ar/(36)Ar value of 143 ± 24, lower than the present-day value of 298.6 (for which (40)Ar has been produced by the radioactive decay of the potassium isotope (40)K, with a half-life of 1.25 billion years; (36)Ar is primordial in origin). This ratio is consistent with an early development of the felsic crust, which might have had an important role in climate variability during the first half of Earth's history.

  12. Volatile Concentrations and H-Isotope Composition of Unequilibrated Eucrites

    NASA Technical Reports Server (NTRS)

    Sarafian, Adam R.; Nielsen, Sune G.; Marschall, Horst R.; Gaetani, Glenn A.; Hauri, Erik H.; Righter, Kevin; Berger, Eve L.

    2017-01-01

    Eucrites are among the oldest and best studied asteroidal basalts (1). They represent magmatism that occurred on their parent asteroid, likely 4-Vesta, starting at 4563 Ma and continuing for approx. 30 Myr. Two hypotheses are debated for the genesis of eucrites, a magma ocean model (2), and a mantle partial melting model. In general, volatiles (H, C, F, Cl) have been ignored for eucrites and 4-Vesta, but solubility of wt% levels of H2O are possible at Vestan interior PT conditions. Targeted measurements on samples could aid our understanding considerably. Recent studies have found evidence of volatile elements in eucrites, but quantifying the abundance of volatiles remains problematic (6). Volatile elements have a disproportionately large effect on melt properties and phase stability, relative to their low abundance. The source of volatile elements can be elucidated by examining the hydrogen isotope ratio (D/H), as different H reservoirs have drastically different H isotope compositions. Recent studies of apatite in eucrites have shown that the D/H of 4-Vesta matches that of Earth and carbonaceous chondrites, however, the D/H of apatites may not represent the D/H of a primitive 4-Vesta melt due to the possibility of degassing prior to the crystallization of apatite. Therefore, the D/H of early crystallizing phases must be measured to determine if the D/H of 4-Vesta is equal to that of the Earth and carbonaceous chondrites.

  13. Relation between isotopic composition of precipitation and atmospheric circulation patterns

    NASA Astrophysics Data System (ADS)

    Brenčič, Mihael; Kononova, Nina K.; Vreča, Polona

    2015-10-01

    Precipitation generating processes depend on atmospheric circulation patterns and consequently it is expected that its water stable isotopic composition of hydrogen and oxygen is related to them. Precipitation generated at similar atmospheric circulation patterns should have similar empirical distribution of δ2H and δ18O values. Mathematical model based on the linear combination of δ2H and δ18O values and on precipitation amount weighted average related to elementary air circulation mechanisms - ECM is proposed. The model enables estimation of average δ2H and δ18O values and their standard deviation for the precipitation generated at distinctive atmospheric circulation patterns. Approach in which atmospheric circulation patterns were classified as ECM based on the Dzerdzeevskii classification was applied. Application of the model is illustrated on the long term precipitation record from Ljubljana GNIP station Slovenia. Estimated values of the parameters for empirical distributions of δ2H and δ18O of each ECM subtype have shown that calculated estimates are reasonable. Further applications of the proposed model enable new insight into the understanding of isotopes spatial and temporal distribution in precipitation important also for better understanding of climate proxies.

  14. The concentration and isotopic composition of osmium in the oceans

    NASA Astrophysics Data System (ADS)

    Sharma, M.; Papanastassiou, D. A.; Wasserburg, G. J.

    1997-08-01

    Osmium is one of the rarer elements in seawater. Analytical difficulties have previously prevented the direct measurement of the osmium concentration and isotopic composition in seawater. We report a chemical separation procedure that yields quantitative extraction of osmium standard and of osmium tracer by iron hydroxide precipitation from seawater doped with osmium standard, osmium tracer, and FeCl 3. The iron hydroxide precipitate is processed to extract osmium, using techniques developed for iron meteorites. Utilizing this procedure, water samples from the Pacific and Atlantic oceans were analyzed for osmium concentration and isotopic composition. Direct determination of the osmium concentration of seawater gives between 15 and 19 fM kg -1. Detailed experiments on different aliquots of one seawater sample from the North Atlantic Ocean, keeping the amounts of reagents constant, yield concentrations from 16 to 19 fM kg -1. The variability in concentration is outside the uncertainty introduced because of blanks and indicates a lack of full equilibration between the osmium tracer and seawater osmium. The most reliable osmium concentration of the North Atlantic deep ocean water is 19 fM kg -1 with the 187Os 186Os ratio being 8.7 ± 0.2 (2σ). Detailed experiments on one seawater sample from the Central Pacific Ocean indicate that the most reliable osmium concentration of the deep ocean water from the Central Pacific is 19 fM kg -1 with the 187Os 186Os ratio being 8.7 ± 0.3 (2σ). The directly measured osmium isotopic composition of the oceans is in good agreement with that obtained from the analysis of some rapidly accumulating organic rich sediments ( Ravizza and Turekian, 1992). A sample of ambient seawater around the Juan de Fuca Ridge gave 187Os 186Os= 6.9 ± 0.4. This is distinctly lower than the deep-sea water value and may reflect local hydrothermal activity or some analytical difficulty with this sample. The osmium isotopic composition of the deep oceans

  15. The elemental and isotopic composition of galactic cosmic ray nuclei

    NASA Technical Reports Server (NTRS)

    Mewaldt, R. A.

    1983-01-01

    A directly accessible sample of matter which originates outside the solar system is provided by galactic cosmic rays. The present investigation is primarily concerned with progress related to questions raised regarding the similarity or difference between solar system matter and matter coming from outside the solar system. The investigation takes into account U.S. contributions to this topic over the period from 1979 to 1982. The cosmic ray (CR) abundances of all the elements from H to Ni (atomic number Z=1 to 28) have now been measured. Cosmic ray source (CRS) and solar system (SS) elemental compositions are listed in a table, and the ratio of CRS to SS abundance for 21 elements is shown in a graph. There is now clear evidence from CR isotope studies that the nucleosynthesis of CRS material has differed from that of SS material.

  16. Isotopic composition of a sample enriched in 93Zr

    DOE PAGES

    Fujii, Toshiyuki; Hori, Jun-ichi; Du, Miting; ...

    2015-10-22

    A project to determine the neutron-capture cross section of long lived fission products and minor actinides has been started by using a beam-line at Japan Proton Accelerator Research Complex (J-PARC). We prepared one of the target nuclides is Zr-93, which in Oak Ridge National Laboratory. Qualitative and quantitative analyses on the sample were performed at Kyoto University. The isotopic composition of (m) Zr (m 90, 91, 92, 93, 94, and 96) was precisely determined by multi-collector thermal ionization mass spectrometry with < 0.1 % of 2 sigma uncertainty. We determined that the atomic abundance of Zr-93 in the sample tomore » be 18.86 ± A 0.05 %.« less

  17. Chemical composition of HAL, an isotopically-unusual Allende inclusion

    NASA Technical Reports Server (NTRS)

    Davis, A. M.; Tanaka, T.; Grossman, L.; Lee, T.; Wasserburg, G. J.

    1982-01-01

    Samples of hibonite, black rim, and portions of friable rim from an unusual Allende inclusion, named HAL, were analyzed by INAA and RNAA for 37 major, minor, and trace elements. An unusually low amount of Ce was found in HAL, although it otherwise was highly enriched in REE compared to C1 chondrites. HAL is also depleted in Sr, Ba, U, V, Ru, Os, and Ir relative to other refractory elements. It is concluded that the distribution of REE between hibonite and rims was established when hibonite and other refractory minerals were removed at slightly different temperatures from a hot, oxidizing gas in which they previously coexisted as separate grains. Possible locations for the chemical and mass dependent isotopic fractionation are considered to be in ejecta from the low temperature helium-burning zone of a supernova and in the locally oxidizing environment generated by evaporation of interstellar grains of near-chondritic chemical composition.

  18. Baseline shifts in coral skeletal oxygen isotopic composition: a signature of symbiont shuffling?

    NASA Astrophysics Data System (ADS)

    Carilli, J. E.; Charles, C. D.; Garren, M.; McField, M.; Norris, R. D.

    2013-06-01

    Decades-long records of the stable isotopic composition of coral skeletal cores were analyzed from four sites on the Mesoamerican Reef. Two of the sites exhibited baseline shifts in oxygen isotopic composition after known coral bleaching events. Changes in pH at the calcification site caused by a change in the associated symbiont community are invoked to explain the observed shift in the isotopic composition. To test the hypothesis that changes in symbiont clade could affect skeletal chemistry, additional coral samples were collected from Belize for paired Symbiodinium identification and skeletal stable isotopic analysis. We found some evidence that skeletal stable isotopic composition may be affected by symbiont clade and suggest this is an important topic for future investigation. If different Symbiodinium clades leave consistent signatures in skeletal geochemical composition, the signature will provide a method to quantify past symbiont shuffling events, important for understanding how corals are likely to respond to climate change.

  19. The silicon isotopic composition of the Ganges and its tributaries

    NASA Astrophysics Data System (ADS)

    Fontorbe, Guillaume; De La Rocha, Christina L.; Chapman, Hazel J.; Bickle, Michael J.

    2013-11-01

    The silicon isotopic composition (δSi30) of the headwaters of the Ganges River, in the Himalaya, ranged from +0.49±0.01‰ to +2.17±0.04‰ at dissolved silicon (DSi) concentrations of 38 to 239 μM. Both the concentration and isotopic composition of DSi in the tributaries increased between the highest elevations to where the Ganges leaves the Himalayas at Rishikesh. The tributaries exhibit a linear correlation between δSi30 and DSi that may represent mixing between a low DSi, low δSi30 (e.g., 40 μM, +0.5‰) component potentially reflecting fractionation during adsorption of a small fraction of silicon onto iron oxides and a high DSi, high δSi30 component (e.g., 240 μM, +1.7‰) produced during higher intensity weathering with a greater proportional sequestration of weathered silicon into secondary minerals or biogenic silica. On the Ganges alluvial plain, in the Ganges and the Yamuna, Gomati, and their tributaries, DSi ranged from 122 to 218 μM while δSi30 ranged from +1.03±0.03‰ to +2.46±0.06‰. Highest values of δSi30 occurred in the Gomati and its tributaries. In general, the lower DSi and higher δSi30 of DSi in these rivers suggests control of both by removal of DSi by secondary mineral formation and/or biogenic silica production. A simple 1-dimensional model with flow through a porous medium is introduced and provides a useful framework for understanding these results.

  20. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  1. Zinc isotopic composition of iron meteorites: Absence of isotopic anomalies and origin of the volatile element depletion

    NASA Astrophysics Data System (ADS)

    Chen, Heng; Nguyen, Bach Mai; Moynier, Frédéric

    2013-12-01

    High-precision Zn isotopic compositions measured by MC-ICP-MS are documented for 32 iron meteorites from various fractionally crystallized and silicate-bearing groups. The δ66Zn values range from -0.59‰ up to +5.61‰ with most samples being slightly enriched in the heavier isotopes compared with carbonaceous chondrites (0 < δ66Zn < 0.5). The δ66Zn versus δ68Zn plot of all samples defines a common linear fractionation line, which supports the hypothesis that Zn was derived from a single reservoir or from multiple reservoirs linked by mass-dependent fractionation processes. Our data for Redfields fall on a mass fractionation line and therefore refute a previous claim of it having an anomalous isotopic composition due to nonmixing of nucleosynthetic products. The negative correlation between δ66Zn and the Zn concentration of IAB and IIE is consistent with mass-dependent isotopic fractionation due to evaporation with preferential loss of lighter isotopes in the vapor phase. Data for the Zn concentrations and isotopic compositions of two IVA samples demonstrate that volatile depletion in the IVA parent body is not likely the result of evaporation. This is important evidence that favors the incomplete condensation origin for the volatile depletion of the IVA parent body.

  2. Variations of the isotopic composition of sulfur in enstatite and ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Gao, Xia; Thiemens, Mark H.

    1993-01-01

    High-precision sulfur isotopic analyses (delta S-33, delta S-34, and delta S-36) of bulk ordinary and enstatite chondrites demonstrate that systematic variations exist. The average delta S-34 values are -0.26 +/- 0.07, -0.02 +/- 0.06, and 0.49 +/- 0.16 percent for enstatite and ordinary and carbonaceous chondrites, respectively. Isotopic variations of different sample specimens of primitive meteorites, e.g., Qingzhen and Abee, were observed which may be attributed to heterogeneity in the early solar nebula. Sulfur isotopic fractionations in both bulk samples and mineral separates are mass-dependent, and no nuclear isotopic anomalies were detected. The sulfur isotopic compositions of both mineral and density separates were measured. The sulfur isotopic compositions of separated chondrules from Chainpur and Bjurbole are reported. Significant isotopic difference for the chondrules from the bulk meteorite are noted for both meteorites.

  3. Precise determination of the absolute isotopic abundance ratio and the atomic weight of chlorine in three international reference materials by the positive thermal ionization mass spectrometer-Cs2Cl+-graphite method.

    PubMed

    Wei, Hai-Zhen; Jiang, Shao-Yong; Xiao, Ying-Kai; Wang, Jun; Lu, Hai; Wu, Bin; Wu, He-Pin; Li, Qing; Luo, Chong-Guang

    2012-12-04

    Because the variation in chlorine isotopic abundances of naturally occurring chlorine bearing substances is significant, the IUPAC Inorganic Chemistry Division, Commission on Isotopic Abundances and Atomic Weights (CIAAW-IUPAC) decided that the uncertainty of atomic weight of chlorine (A(r)(Cl)) should be increased so that the implied range was related to terrestrial variability in 1999 (Coplen, T. B. Atomic weights of the elements 1999 (IUPAC Technical Report), Pure Appl. Chem.2001, 73(4), 667-683; and then, it emphasized that the standard atomic weights of ten elements including chlorine were not constants of nature but depend upon the physical, chemical, and nuclear history of the materials in 2009 (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396). According to the agreement by CIAAW that an atomic weight could be defined for one specified sample of terrestrial origin (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396), the absolute isotope ratios and atomic weight of chlorine in standard reference materials (NIST 975, NIST 975a, ISL 354) were accurately determined using the high-precision positive thermal ionization mass spectrometer (PTIMS)-Cs(2)Cl(+)-graphite method. After eliminating the weighing error caused from evaporation by designing a special weighing container and accurately determining the chlorine contents in two highly enriched Na(37)Cl and Na(35)Cl salts by the current constant coulometric titration, one series of gravimetric synthetic mixtures prepared from two highly enriched Na(37)Cl and Na(35)Cl salts was used to calibrate two thermal ionization mass spectrometers in two individual laboratories. The correction factors (i.e., K(37/35) = R(37/35meas)/R(37/35calc)) were obtained from five cycles of iterative calculations on the basis of calculated and determined R((37)Cl/(35)Cl) values in gravimetric synthetic mixtures. The absolute R((37)Cl/(35)Cl) ratios for NIST SRM 975, NIST 975a, and ISL 354 by the precise

  4. Absolute Proteome Composition and Dynamics during Dormancy and Resuscitation of Mycobacterium tuberculosis.

    PubMed

    Schubert, Olga T; Ludwig, Christina; Kogadeeva, Maria; Zimmermann, Michael; Rosenberger, George; Gengenbacher, Martin; Gillet, Ludovic C; Collins, Ben C; Röst, Hannes L; Kaufmann, Stefan H E; Sauer, Uwe; Aebersold, Ruedi

    2015-07-08

    Mycobacterium tuberculosis remains a health concern due to its ability to enter a non-replicative dormant state linked to drug resistance. Understanding transitions into and out of dormancy will inform therapeutic strategies. We implemented a universally applicable, label-free approach to estimate absolute cellular protein concentrations on a proteome-wide scale based on SWATH mass spectrometry. We applied this approach to examine proteomic reorganization of M. tuberculosis during exponential growth, hypoxia-induced dormancy, and resuscitation. The resulting data set covering >2,000 proteins reveals how protein biomass is distributed among cellular functions during these states. The stress-induced DosR regulon contributes 20% to cellular protein content during dormancy, whereas ribosomal proteins remain largely unchanged at 5%-7%. Absolute protein concentrations furthermore allow protein alterations to be translated into changes in maximal enzymatic reaction velocities, enhancing understanding of metabolic adaptations. Thus, global absolute protein measurements provide a quantitative description of microbial states, which can support the development of therapeutic interventions.

  5. Tooth enamel maturation reequilibrates oxygen isotope compositions and supports simple sampling methods

    NASA Astrophysics Data System (ADS)

    Trayler, Robin B.; Kohn, Matthew J.

    2017-02-01

    Oxygen isotope and major element zoning patterns of several disparate ungulate teeth were collected to evaluate the timing and geometry of enamel formation, records of isotope zoning, and tooth enamel sampling strategies. Isotopic zoning in mammalian tooth enamel encodes a sub-annual time series of isotopic variation of an animal's body water composition, with a damping factor that depends on the specifics of how enamel mineralizes. Enamel formation comprises two stages: precipitation of appositional enamel with a high CO3:PO4 ratio, followed by precipitation of maturational enamel with a lower CO3:PO4. If appositional and maturational enamel both contribute to isotope compositions (but with different CO3:PO4), and if isotope compositions vary seasonally, paired δ18O values from CO3 and PO4 profiles should show a spatial separation. CO3 isotope patterns should be shifted earlier seasonally than PO4 isotope patterns. Such paired profiles for new and published data show no resolvable shifts, i.e. CO3 and PO4 δ18O profiles show coincident maxima and minima. This coincidence suggests that enamel maturation reequilibrates appositional isotope compositions. If enamel maturation establishes enamel isotope compositions, the geometry of maturation, not apposition, should be considered when devising sampling protocols. X-ray maps of Ca zoning show that the majority of enamel (inner and middle layers) mineralizes heavily at a high angle to the external tooth surface and the enamel-dentine junction over length scales of 2-4 mm, while the outer enamel surface mineralizes more slowly. These data suggest that isotopic sampling strategies should parallel maturational geometry and focus on interior enamel to improve data fidelity. The magnitude of isotopic damping is also smaller than implied in previous studies, so tooth enamel zoning more closely reflects original body water isotopic variations than previously assumed.

  6. Novel concept for the mass spectrometric determination of absolute isotopic abundances with improved measurement uncertainty: Part 1 - theoretical derivation and feasibility study

    NASA Astrophysics Data System (ADS)

    Rienitz, Olaf; Pramann, Axel; Schiel, Detlef

    2010-01-01

    The development of a new method for the experimental determination of absolute isotopic abundances using a modified isotope dilution mass spectrometry (IDMS) technique is described. The intention and thus main application will be the quantification of molar masses M of highly enriched materials with improved measurement uncertainty (Urel(M) [approximate] 10-8 with k = 2). In part 1 of the current work, the theoretical foundation of the new method and its mathematical derivation is shown in detail, while part 2 will cover the experiments based on the new method described. Its core idea is the introduction of a virtual element (VE) consisting of all isotopes but the one having the largest or smallest abundance. IDMS is used to determine the mass fraction of this VE in its matrix, namely the element itself. A new set of equations serve to calculate all isotopic abundances (even the large one omitted with the introduction of the VE) merely from the mass fraction of the VE. A comprehensive uncertainty budget according to the Guide to the Expression of Uncertainty in Measurement (GUM) was set up in order to discuss and validate the novel concept. The hypothetical input data of the uncertainty budget were estimated to resemble a silicon material highly enriched with respect to 28Si used in the context of the international Avogadro Project. Considering the calculated results, the experimental determination of the molar mass of the above mentioned silicon seems very promising. As far as the authors know, this will be the first time IDMS was applied to determine a molar mass.

  7. Isotopic and Elemental Composition of Roasted Coffee as a Guide to Authenticity and Origin.

    PubMed

    Carter, James F; Yates, Hans S A; Tinggi, Ujang

    2015-06-24

    This study presents the stable isotopic and elemental compositions of single-origin, roasted coffees available to retail consumers. The δ(13)C, δ(15)N, and δ(18)O compositions were in agreement with those previously reported for green coffee beans. The δ(15)N composition was seen to be related to organic cultivation, reflected in both δ(2)H and δ(18)O compositions. The δ(13)C composition of extracted caffeine differed little from that of the bulk coffee. Stepwise discriminant analysis with jackknife tests, using isotopic and elemental data, provided up to 77% correct classification of regions of production. Samples from Africa and India were readily classified. The wide range in both isotopic and elemental compositions of samples from other regions, specifically Central/South America, resulted in poor discrimination between or within these regions. Simpler X-Y and geo-spatial plots of the isotopic data provided effective visual means to distinguish between coffees from different regions.

  8. Light element isotopic compositions of cometary matter returned by the STARDUST mission

    SciTech Connect

    McKeegan, K D; Aleon, J; Bradley, J; Brownlee, D; Busemann, H; Butterworth, A; Chaussidon, M; Fallon, S; Floss, C; Gilmour, J; Gounelle, M; Graham, G; Guan, Y; Heck, P R; Hoppe, P; Hutcheon, I D; Huth, J; Ishii, H; Ito, M; Jacobsen, S B; Kearsley, A; Leshin, L A; Liu, M; Lyon, I; Marhas, K; Marty, B; Matrajt, G; Meibom, A; Messenger, S; Mostefaoui, S; Nakamura-Messenger, K; Nittler, L; Palma, R; Pepin, R O; Papanastassiou, D A; Robert, F; Schlutter, D; Snead, C J; Stadermann, F J; Stroud, R; Tsou, P; Westphal, A; Young, E D; Ziegler, K; Zimmermann, L; Zinner, E

    2006-10-10

    Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild2 particle fragments, however extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Non-terrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is {sup 16}O-enriched like refractory inclusions in meteorites, suggesting formation in the hot inner solar nebula and large-scale radial transport prior to comet accretion in the outer solar system.

  9. Sulphur isotope compositions of components of coal and S-isotope fractionation during its combustion and flue gas desulphurization.

    PubMed

    Derda, Małorzata; Chmielewski, Andrzej Grzegorz; Licki, Janusz

    2007-03-01

    Sulphur isotope compositions were determined in two different Polish coals (hard coal and lignite) and by-products originating from their combustion. The desulphurization process was also investigated. It was demonstrated that desulphurization changes the isotopic composition of sulphur emitted in the form of SO(2) to the atmosphere even if the process is conducted in a different way (wet lime technology and electron beam method). This fact has to be considered in the studies regarding anthropogenic sulphur genesis and its fate in the environment.

  10. Herbivore tooth oxygen isotope compositions: Effects of diet and physiology

    NASA Astrophysics Data System (ADS)

    Kohn, Matthew J.; Schoeninger, Margaret J.; Valley, John W.

    1996-10-01

    The applicability of rapid and precise laser probe analysis of tooth enamel for δ18O has been verified, and the method has been applied to different modern herbivores in East Africa. Sampling and pretreatment procedures involve initial bleaching and grinding of enamel to <75 μm, and elimination of adsorbed water and organic compounds with BrF 5. Typical analytical reproducibilities for 0.5-2 mg samples are ±0.08‰ (± 1σ). Chemical and spectroscopic characterization of pretreated but unanalyzed samples show no alteration compared to fresh enamel. Solid reaction products are nearly pure CaF 2 with little evidence for residual O 2. Because laser probe fluorination extracts oxygen from all sites in the apatite structure (phosphate, structural carbonate, and hydroxyl), only unaltered tooth enamel (>95% apatite) can be analyzed reliably. Different East African herbivores exhibit previously unsuspected compositional differences. Average enamel δ18O values (V-SMOW) are approximately: 25‰ (goat), 27‰ (oryx), 28‰ (dikdik and zebra), 29‰ (topi), 30‰ (gerenuk), and 32‰ (gazelle). These compositions differ from generalized theoretical models, but are broadly consistent with expected isotope effects associated with differences in how much each animal (a) drinks, (b) eats C3 vs. C4 plants, and (c) pants vs. sweats. Consideration of diet, water turnover, and animal physiology will allow the most accurate interpretation of ancient teeth and targeting of environmentally-sensitive animals in paleoclimate studies.

  11. NEW INSIGHTS ON SATURN'S FORMATION FROM ITS NITROGEN ISOTOPIC COMPOSITION

    SciTech Connect

    Mousis, Olivier; Lunine, Jonathan I.; Fletcher, Leigh N.; Mandt, Kathleen E.; Ali-Dib, Mohamad; Atreya, Sushil

    2014-12-01

    The recent derivation of a lower limit for the {sup 14}N/{sup 15}N ratio in Saturn's ammonia, which is found to be consistent with the Jovian value, prompted us to revise models of Saturn's formation using as constraints the supersolar abundances of heavy elements measured in its atmosphere. Here we find that it is possible to account for both Saturn's chemical and isotopic compositions if one assumes the formation of its building blocks at ∼45 K in the protosolar nebula, provided that the O abundance was ∼2.6 times protosolar in its feeding zone. To do so, we used a statistical thermodynamic model to investigate the composition of the clathrate phase that formed during the cooling of the protosolar nebula and from which the building blocks of Saturn were agglomerated. We find that Saturn's O/H is at least ∼34.9 times protosolar and that the corresponding mass of heavy elements (∼43.1 M {sub ⊕}) is within the range predicted by semi-convective interior models.

  12. Investigating Tungsten Concentrations and Isotopic Compositions of Natural Water Samples from the Carson River Basin

    NASA Astrophysics Data System (ADS)

    Wasserman, N. L.; Williams, R. W.; Kayzar, T. M.; Schorzman, K. C.

    2012-12-01

    Recent studies have shown that W-isotopes may fractionate in nature1; however, the magnitude and cause of the isotopic variations are largely unknown and unconstrained. In this study, the isotopic compositions of the NIST 3163 W standard, W ore minerals, and 15 natural surface waters from Nevada's Carson River Basin were analyzed by MC-ICP-MS using external bracketing with NIST 3163 and the IUPAC 184W/183W for mass bias correction. Chemical separation procedures were developed to purify W from natural matrices and tested to assure fractionation was not introduced during column chemistry. The W isotopic compositions of these samples were measured and compared to the accepted IUPAC composition of natural W. Samples of wolframite (Fe, MnWO4) and hubnerite (MnWO4) have compositions similar to the IUPAC value but vary from the isotopic composition of NIST 3163 - particularly in 182W/183W. The isotopic compositions of the natural waters, except for an extremely evaporated sample from Soda Lake, are similar to the NIST standard. This evaporative lake, formed by a maar, has a unique chemical composition compared to other surface waters with high W (800 ± 20 ng/g) and As (1665 ± 17 ng/g) concentrations; and relatively low Fe (5.00 ± 0.13 ng/g) and Mn (0.52 ± 0.07 ng/g). These results support recent observations of natural W isotopic variation and imply that W-isotope compositions may be useful for environmental applications of stable isotope geochemistry. 1. Irisawa, K. and Hirata, T. (2006) Tungsten isotopic analysis on six geochemical reference materials using multiple collector-ICP-mass spectrometry coupled with a rhenium-external correction technique. Journal of Analytical Atomic Spectrometry 21, 1387-1395.

  13. Tungsten isotope composition of the Acasta Gneiss Complex

    NASA Astrophysics Data System (ADS)

    Willbold, M.; Mojzsis, S. J.; Chen, H.-W.; Elliott, T.

    2015-06-01

    High-precision tungsten (182W/184W) isotope measurements on well-characterised mafic and felsic samples of the ca. 3960 Ma Acasta Gneiss Complex (AGC; Northwest Territories, Canada) show radiogenic ε182W values between +0.06 to +0.15. Two ca. 3600 Ma felsic samples from this terrane have ε182W ∼ 0 and are the oldest samples so far documented to have a W isotopic composition indistinguishable from that of the modern mantle. The ε182W data are correlated with ε142Nd (Roth et al., 2014) and we attribute this variability to incomplete metamorphic homogenisation of the 3960 Ma protolith with more recent material in a 3370 Ma tectono-thermal event. Notably, the value of the positive ε182W anomalies seen in the 3960 Ma AGC samples that are least affected by metamorphic homogenisation is comparable to that observed in other early Archean rocks (Isua Supracrustal Belt, Greenland; Nuvvuagittuq Supracrustal Belt, Canada) and the late Archean Kostomuksha komatiites (Karelia). This demonstrates a globally constant signature. We infer that the presence of a pre-late veneer mantle represents the most straightforward interpretation of a uniform distribution of ε182W ∼ + 0.15 value in Archean rocks of different ages. We show that such a notion is compatible with independent constraints from highly siderophile element abundances in mafic and ultra-mafic Archean mantle-derived rocks. The absence of anomalous ε182W and ε142Nd so far measured in samples younger than ca. 2800 Ma suggests progressive convective homogenisation of silicate reservoirs. The downward mixing of an upper mantle rich in late-delivered meteoritic material might account for these combined observations.

  14. Non-chondritic sulphur isotope composition of the terrestrial mantle.

    PubMed

    Labidi, J; Cartigny, P; Moreira, M

    2013-09-12

    Core-mantle differentiation is the largest event experienced by a growing planet during its early history. Terrestrial core segregation imprinted the residual mantle composition by scavenging siderophile (iron-loving) elements such as tungsten, cobalt and sulphur. Cosmochemical constraints suggest that about 97% of Earth's sulphur should at present reside in the core, which implies that the residual silicate mantle should exhibit fractionated (34)S/(32)S ratios according to the relevant metal-silicate partition coefficients, together with fractionated siderophile element abundances. However, Earth's mantle has long been thought to be both homogeneous and chondritic for (34)S/(32)S, similar to Canyon Diablo troilite, as it is for most siderophile elements. This belief was consistent with a mantle sulphur budget dominated by late-accreted chondritic components. Here we show that the mantle, as sampled by mid-ocean ridge basalts from the south Atlantic ridge, displays heterogeneous (34)S/(32)S ratios, directly correlated to the strontium and neodymium isotope ratios (87)Sr/(86)Sr and (143)Nd/(144)Nd. These isotope trends are compatible with binary mixing between a low-(34)S/(32)S ambient mantle and a high-(34)S/(32)S recycled component that we infer to be subducted sediments. The depleted end-member is characterized by a significantly negative δ(34)S of -1.28 ± 0.33‰ that cannot reach a chondritic value even when surface sulphur (from continents, altered oceanic crust, sediments and oceans) is added. Such a non-chondritic (34)S/(32)S ratio for the silicate Earth could be accounted for by a core-mantle differentiation record in which the core has a (34)S/(32)S ratio slightly higher than that of chondrites (δ(34)S = +0.07‰). Despite evidence for late-veneer addition of siderophile elements (and therefore sulphur) after core formation, our results imply that the mantle sulphur budget retains fingerprints of core-mantle differentiation.

  15. Climatic influences on the oxygen isotopic composition of biogenic silica in prairie grass

    NASA Astrophysics Data System (ADS)

    Webb, Elizabeth A.; Longstaffe, Fred J.

    2002-06-01

    Samples of Calamovilfa longifolia were collected from across the North American prairies to investigate the relationship between the oxygen-isotope composition of biogenic silica (phytoliths) deposited in this grass and relative humidity, temperature, and the oxygen-18 enrichment of soil water relative to local precipitation. The δ 18O values of silica in nontranspiring tissues were controlled by soil-water composition and temperature, whereas the oxygen-18 content of silica formed in leaf and inflorescence tissues was enriched further by transpiration. Accurate calculation of growing temperature was possible only when the oxygen-isotope compositions of both stem silica and soil water were known. However, the oxygen-isotope values of stem phytoliths can be used to calculate the variation in the isotopic composition of soil water across a North American temperature gradient. As plant organic matter decays and phytoliths are transferred to the soil, the temperature and soil-water signals carried by the oxygen-isotope composition of silica from nontranspiring tissues can be masked by the oxygen-18 enrichment of phytoliths from transpiring tissues. However, the overall oxygen-isotope composition of a soil-phytolith assemblage can be related to temperature using an empirical relationship based on temperature and the difference between soil-phytolith and estimated soil-water oxygen-isotope compositions.

  16. Controls on the stable isotope compositions of travertine from hyperalkaline springs in Oman: Insights from clumped isotope measurements

    NASA Astrophysics Data System (ADS)

    Falk, E. S.; Guo, W.; Paukert, A. N.; Matter, J. M.; Mervine, E. M.; Kelemen, P. B.

    2016-11-01

    Carbonate formation at hyperalkaline springs is typical of serpentinization in peridotite massifs worldwide. These travertines have long been known to exhibit large variations in their carbon and oxygen isotope compositions, extending from apparent equilibrium values to highly depleted values. However, the exact causes of these variations are not well constrained. We analyzed a suite of well-characterized fresh carbonate precipitates and travertines associated with hyperalkaline springs in the peridotite section of the Samail ophiolite, Sultanate of Oman, and found their clumped isotope compositions vary systematically with formation environments. Based on these findings, we identified four main processes controlling the stable isotope compositions of these carbonates. These include hydroxylation of CO2, partial isotope equilibration of dissolved inorganic carbon, mixing between isotopically distinct carbonate end-members, and post-depositional recrystallization. Most notably, in fresh crystalline films on the surface of hyperalkaline springs and in some fresh carbonate precipitates from the bottom of hyperalkaline pools, we observed large enrichments in Δ47 (up to ∼0.2‰ above expected equilibrium values) which accompany depletions in δ18O and δ13C, yielding about 0.01‰ increase in Δ47 and 1.1‰ decrease in δ13C for every 1‰ decrease in δ18O, relative to expected equilibrium values. This disequilibrium trend, also reflected in preserved travertines ranging in age from modern to ∼40,000 years old, is interpreted to arise mainly from the isotope effects associated with the hydroxylation of CO2 in high-pH fluids and agrees with our first-order theoretical estimation. In addition, in some fresh carbonate precipitates from the bottom of hyperalkaline pools and in subsamples of one preserved travertine terrace, we observed additional enrichments in Δ47 at intermediate δ13C and δ18O, consistent with mixing between isotopically distinct carbonate end

  17. The iron isotope composition of enstatite meteorites: Implications for their origin and the metal/sulfide Fe isotopic fractionation factor

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Savage, Paul S.; Moynier, Frédéric

    2014-10-01

    Despite their unusual chemical composition, it is often proposed that the enstatite chondrites represent a significant component of Earth’s building materials, based on their terrestrial similarity for numerous isotope systems. In order to investigate a possible genetic relationship between the Fe isotope composition of enstatite chondrites and the Earth, we have analyzed 22 samples from different subgroups of the enstatite meteorites, including EH and EL chondrites, aubrites (main group and Shallowater) and the Happy Canyon impact melt. We have also analyzed the Fe isotopic compositions of separated (magnetic and non-magnetic) phases from both enstatite chondrites and achondrites. On average, EH3-5 chondrites (δ56Fe = 0.003 ± 0.042‰; 2 standard deviation; n = 9; including previous literature data) as well as EL3 chondrites (δ56Fe = 0.030 ± 0.038‰; 2 SD; n = 2) have identical and homogeneous Fe isotopic compositions, indistinguishable from those of the carbonaceous chondrites and average terrestrial peridotite. In contrast, EL6 chondrites display a larger range of isotopic compositions (-0.180‰ < δ56Fe < 0.181‰; n = 11), a result of mixing between isotopically distinct mineral phases (metal, sulfide and silicate). The large Fe isotopic heterogeneity of EL6 is best explained by chemical/mineralogical fragmentation and brecciation during the complex impact history of the EL parent body. Enstatite achondrites (aubrites) also exhibit a relatively large range of Fe isotope compositions: all main group aubrites are enriched in the light Fe isotopes (δ56Fe = -0.170 ± 0.189‰; 2 SD; n = 6), while Shallowater is, isotopically, relatively heavy (δ56Fe = 0.045 ± 0.101‰; 2 SD; n = 4; number of chips). We take this variation to suggest that the main group aubrite parent body formed a discreet heavy Fe isotope-enriched core, whilst the Shallowater meteorite is most likely from a different parent body where core and silicate material remixed. This could be

  18. Hydrogen and oxygen in brine shrimp chitin reflect environmental water and dietary isotopic composition

    NASA Astrophysics Data System (ADS)

    Nielson, Kristine E.; Bowen, Gabriel J.

    2010-03-01

    Hydrogen and oxygen isotope ratios of the common structural biopolymer chitin are a potential recorder of ecological and environmental information, but our understanding of the mechanisms of incorporation of H and O from environmental substrates into chitin is limited. We report the results of a set of experiments in which the isotopic compositions of environmental water and diet were varied independently in order to assess the contribution of these variables to the H and O isotopic composition of Artemia franciscana chitin. Hydrogen isotope ratios of chitin were strongly linearly correlated with both food and water, with approximately 26% of the hydrogen signal reflecting food and approximately 38% reflecting water. Oxygen isotopes were also strongly correlated with the isotopic composition of water and food, but whereas 69% of oxygen in chitin exchanged with environmental water, only 10% was derived from food. We propose that these observations reflect the position-specific, partial exchange of H and O atoms with brine shrimp body water during the processes of digestion and chitin biosynthesis. Comparison of culture experiments with a set of natural samples collected from the Great Salt Lake, UT in 2006 shows that, with some exceptions, oxygen isotope compositions of chitin track those of water, whereas hydrogen isotopes vary inversely with those of lake water. The different behavior of the two isotopic systems can be explained in terms of a dietary shift from allochthonous particulate matter with relatively higher δ 2H values in the early spring to autochthonous particulate matter with significantly lower δ 2H values in the late summer to autumn. These results suggest oxygen in chitin may be a valuable proxy for the oxygen isotopic composition of environmental water, whereas hydrogen isotope values from the same molecule may reveal ecological and biogeochemical changes within lakes.

  19. Herbivore tooth oxygen isotope compositions: Effects of diet and physiology

    SciTech Connect

    Kohn, M.J.; Valley, J.W.; Schoeninger, M.J.

    1996-10-01

    The applicability of rapid and precise laser probe analysis of tooth enamel for {delta}{sup 18}O has been verified, and the method has been applied to different modern herbivores in East Africa. Sampling and pretreatment procedures involve initial bleaching and grinding of enamel to <75 {mu}m, and elimination of adsorbed water and organic compounds with BrF{sub 5}. Typical analytical reproducibilities for 0.5-2 mg samples are {+-}0.08{per_thousand} ({+-} 1{sigma}). Chemical and spectroscopic characterization of pretreated but unanalyzed samples show no alteration compared to fresh enamel. Solid reaction products are nearly pure CaF{sub 2} with little evidence for residual O{sub 2}. Because laser probe fluorination extracts oxygen from all sites in the apatite structure (phosphate, structural carbonate, and hydroxyl), only unaltered tooth enamel ( >95% apatite) can be analyzed reliably. Different East African herbivores exhibit previously unsuspected compositional differences. Average enamel {delta}{sup 18}O values (V-SMOW) are approximately: 25{per_thousand} (goat). 27{per_thousand} (oryx), 28{per_thousand} (dikdik and zebra), 29{per_thousand} (topi), 30{per_thousand} (gerenuk), and 32{per_thousand} (gazelle). These compositions differ from generalized theoretical models, but are broadly consistent with expected isotope effects associated with differences in how much each animal (a) drinks, (b) eats C3 vs. C4 plants, and (c) pants vs. sweats. Consideration of diet, water turnover. and animal physiology will allow the most accurate interpretation of ancient teeth and targeting of environmentally-sensitive animals in paleoclimate studies. 66 refs., 2 figs., 2 tabs.

  20. On the equilibrium isotopic composition of the thorium-uranium-plutonium fuel cycle

    NASA Astrophysics Data System (ADS)

    Marshalkin, V. Ye.; Povyshev, V. M.

    2016-12-01

    The equilibrium isotopic compositions and the times to equilibrium in the process of thorium-uranium-plutonium oxide fuel recycling in VVER-type reactors using heavy water mixed with light water are estimated. It is demonstrated thEhfat such reactors have a capacity to operate with self-reproduction of active isotopes in the equilibrium mode.

  1. Soil drying effects on the carbon isotope composition of soil respiration

    EPA Science Inventory

    Stable isotopes are used widely as a tool for determining sources of carbon (C) fluxes in ecosystem C studies. Environmental factors that change over time, such as moisture, can create dynamic changes in the isotopic composition of C assimilated by plants, and offers a unique opp...

  2. Terrestrial and Meteorite Carbon Appear to Have the Same Isotopic Composition

    PubMed Central

    Libby, W. F.

    1971-01-01

    The carbon-isotope ratio recently obtained for the carbon found in the Murchison meteorite, which has been shown (by the racemic nature of twelve component amino acids) to be free of terrestrial contamination, agrees with that for average terrestrial sediments. This finding indicates that the earth and the stony meteorites contain carbon of the same isotopic composition. PMID:16591904

  3. Isotope composition (C, H, O) and gas potential assessment in the South Caspian depression (Azerbaijan)

    NASA Astrophysics Data System (ADS)

    Poletayev, A. V.

    2009-04-01

    The large amount of HC isotope composition material of over 330 samples allows to study gas potential assessment within the South Caspian depression. Maps of isotope composition changes according to area extent, as well as graphs of HC distribution depending upon stratigraphic age including rocks, graphs of isotope composition change on sampling depth were compiled for HC study and oil-gas deposits formation. Comparison of mud volcanoes gases, oil and gas fields, gas-hydrates and bottom sediments was conducted. Gases genesis according to M. Shoelle and A. James methodic was studied. Model of area paleoconstruction was studied. Comparison of mud volcanoes gases with gases of oil fields within South Caspian depression shows that their isotope composition varies within the same ranges. Their difference is observed in chemical composition. Mud volcanoes gases are sharply impoverished by amount of heavy hydrocarbons. Study of isotope gases composition distribution in extent area allowed to distinguish zones and areas with different composition of heavy isotope. For example, in the deep-seated areas of the South Caspian depression toward flank zones of Low Kura depression as well some areas of Baku archipelago and Absheron peninsula gradually one can observe zones with a low content of heavy carbon isotope etc. Isotope gases composition depending upon stratigraphic age of including rocks has a certain peculiarities. From low to the upper section of PS as well as deposits of Cretaceous system toward chokrak regiostage (underlying PS deposits) one can observe increase of light carbon isotope. This fact allows to suppose that there exits two stages of HC formation. Comparison of HC gases isotope composition with sampling depth allowed to conclude that in the near-flank zones oil-gas deposits were re-formed by a large gas volumes the source of which was there same deposits within new thermobaric conditions. Gases of biochemical, diagenetic and thermocatalytic genesis etc

  4. Monitoring the water vapor isotopic composition in the temperate North Atlantic

    NASA Astrophysics Data System (ADS)

    Steen-Larsen, H. C.; Sveinbjörnsdottir, A. E.; Jónsson, T. H.; Johnsen, S. J.

    2012-04-01

    Water stable isotopes have during many decades been used as climate proxies and indicators for variations in the hydrological cycle. However we are to a great extent still using simple empirical relationships without any deeper theoretical understanding. In order to properly relate changes in the climate and hydrological cycle to changes in the observed stable water isotopic signal we must understand the underlying physical processes. Furthermore it is a challenge for General Climate Models to adequately represent the isotopes in the hydrological cycle because of lack of in-situ measurements of the atmospheric water-vapor composition in the source regions. During the fall of 2010 we installed an autonomous water vapor spectroscopy laser (from Los Gatos Research) in a lighthouse on the South Coast of Iceland (63.83 N 21.47W) with the plan to be operational for several years. The purpose of this installation was through monitoring of the water vapor isotopic composition to understand the physical processes governing the isotopic composition of the water vapor evaporated from the ocean as well as the processes of mixing between the free troposphere and marine boundary layer. Because of the remoteness of the monitoring site and simple topography we are able to isolate the 'fingerprint' on the isotopic signal in the water vapor from respectively the ocean and the interior highland leading to a near perfect case-study area. Using back-trajectories we find a strong influence of the origin of the air masses on the measured isotopic composition. The mixing of the marine-boundary layer is found to strongly influence the measured isotopic composition. The second order isotopic parameter, d-excess, is contrary to theory and previous observations found not to depend on the relative humidity. However we do find a good correlation between the d-excess and the measured isotopic composition. We speculate that the lack of correlation between d-excess and relative humidity can be

  5. The Pb isotopic compositions of lower crustal xenoliths and the evolution of lower crustal Pb

    NASA Astrophysics Data System (ADS)

    Rudnick, Roberta L.; Goldstein, Steven L.

    1990-05-01

    Pb isotopic compositions for three suites of well-characterized granulite facies xenoliths from a diversity of crustal settings (the Chudleigh and McBride volcanic provinces, Queensland, Australia and the Eifel volcanics, West Germany) are presented here. All three suites plot to the right of the 4.57 Ga geochron, similar to the published Pb results of other mafic granulite xenoliths. Correlations between Sr, Nd and Pb isotopes in the three suites measured here point to an origin by mixing of mantle-derived basaltic magmas with lower crust at the time of basaltic underplating (i.e., < 100 Ma for Chudleigh, ˜ 300 Ma for McBride, ˜ 450 Ma for Eifel). Because the Pb concentration of the continental crust is much greater than that of mantle-derived basaltic magmas, the Pb isotopic compositions of the magmas are shifted dramatically by the mixing, allowing delineation of the isotopic characteristics of the lower crust. In all three cases, this lower crust had radiogenic Pb and Sr isotopic compositions and unradiogenic Nd isotopic compositions, yielding Proterozoic Nd model ages. Such radiogenic lower crust contrasts markedly with the Pb isotopic characteristics of most Precambrian granulite facies terrains. Whereas the Nd isotopes reflect the average age of crust formation, the Pb isotopic characteristics of the lower crust appear to be a function of the tectonothermal age of the crust: unradiogenic Pb can only develop in regions which have remained stable for long time periods (e.g., cratons), whereas in areas where orogenies have occurred subsequent to crustal formation, the Pb isotopic composition of the lower crust is "rejuvenated" through mixing with radiogenic Pb from upper crust and mantle-derived magmas. Thus, after orogeny, the Pb isotopic composition of the lower crust resembles that of the upper crust. On the basis of this proposed orogenic age-Pb isotope correlation, we estimate the Pb isotopic composition of the lower crust using the data for granulite

  6. Monitoring the water vapor isotopic composition in the temperate North Atlantic

    NASA Astrophysics Data System (ADS)

    Sveinbjörnsdottir, Arny E.; Steen-Larsen, Hans Christian; Jonsson, Thorsteinn; Johnsen, Sigfus J.

    2013-04-01

    Water stable isotopes have during many decades been used as climate proxies and indicators for variations in the hydrological cycle. However we are to a great extent still using simple empirical relationships without any deeper theoretical understanding. In order to properly relate changes in the climate and hydrological cycle to changes in the observed stable water isotopic signal we must understand the underlying physical processes. Furthermore it is a challenge for General Climate Models to adequately represent the isotopes in the hydrological cycle because of lack of in-situ measurements of the atmospheric water-vapor composition in the source regions. During the fall of 2010 we installed an autonomous water vapor spectroscopy laser (from Los Gatos Research) in a lighthouse on the South Coast of Iceland (63.83 N 21.47W) with the plan to be operational for several years. The purpose of this installation was through monitoring of the water vapor isotopic composition to understand the physical processes governing the isotopic composition of the water vapor evaporated from the ocean as well as the processes of mixing between the free troposphere and marine boundary layer. Because of the remoteness of the monitoring site and simple topography we are able to isolate the 'fingerprint' on the isotopic signal in the water vapor from respectively the ocean and the interior highland leading to a near perfect case-study area. Using back-trajectories we find a strong influence of the origin of the air masses on the measured isotopic composition. The mixing of the marine-boundary layer is found to strongly influence the measured isotopic composition. The second order isotopic parameter, d-excess, is contrary to theory and previous observations found not to depend on the relative humidity. However we do find a good correlation between the d-excess and the measured isotopic composition. We speculate that the lack of correlation between d-excess and relative humidity can be

  7. Titanium and Oxygen Isotope Compositions of Individual Chondrules from Ordinary Chondrites

    NASA Astrophysics Data System (ADS)

    Bauer, K. K.; Schönbächler, M.; Fehr, M. A.; Vennemann, T.; Chaumard, N.; Zanda, B.

    2016-08-01

    We measured Ti and triple-O isotope compositions of individual chondrules (characterized by CT scanning) from ordinary chondrites. We will discuss correlations between Ti and ∆17O and their implication for the origin of nucleosynthetic anomalies.

  8. Isotopic composition of Pb and Th in interplinian volcanics from Somma-Vesuvius volcano, Italy

    USGS Publications Warehouse

    Cortini, M.; Ayuso, R.A.; de Vivo, B.; Holden, P.; Somma, R.

    2004-01-01

    We present a detailed isotopic study of volcanic rocks emitted from Somma-Vesuvius volcano during three periods of interplinian activity: "Protohistoric" (3550 y B.P. to 79 A.D.), "Ancient Historic" (79 to 472 A.D.) and "Medieval" (472 to 1631 A.D.). Pb isotopic compositions of two acid leached fractions and whole rock residues of 37 whole rock samples (determined by Somma et al., 2001) show that each of the three interplinian periods is distinguished by small, systematic, and unique uranogenic and thorogenic Pb isotopic trends. This key and novel feature is compatible with the notion that the Pb isotopic data reflect small-scale source heterogeneity operating over relatively short periods of time. From this representative group of samples, a selected set of nine whole rocks were analysed for Th isotopes. 232Th/238U ratios in the source can be obtained independently from Pb and from Th isotopes. Those obtained from Pb isotopes represent source ratios, time-integrated over the whole age of the Earth; they range from 3.9 to 4.1. 232Th/238U obtained from Th isotopes are those of the present source. They are lower, and cluster around 3.5; this difference probably indicates recent U enrichment of the present source. The behaviour of Pb, as inferred by its isotopic ratios, is quite distinct from that of Sr and Nd isotopes: Pb isotope variations are not correlated to Sr or Nd isotope variations. The isotopic contrast is compatible with the idea that the isotopes were decoupled during magmatic production, evolution, and ascent through the crust. Thus, the Pb isotopes do not reflect the effects of the same processes as in the case of the Sr and Nd isotopes, or, as we also favor, they do not necessarily reflect the same source contributions into the magmas. Moreover, the Pb isotopic evolution of the interplinian rocks chiefly reflects mixing, driven by processes that are superimposed on, and independent of, other source contributions that determine the isotopic compositions

  9. Probing the Crystal Structure, Composition-Dependent Absolute Energy Levels, and Electrocatalytic Properties of Silver Indium Sulfide Nanostructures.

    PubMed

    Saji, Pintu; Ganguli, Ashok K; Bhat, Mohsin A; Ingole, Pravin P

    2016-04-18

    The absolute electronic energy levels in silver indium sulfide (AIS) nanocrystals (NCs) with varying compositions and crystallographic phases have been determined by using cyclic voltammetry. Different crystallographic phases, that is, metastable cubic, orthorhombic, monoclinic, and a mixture of cubic and orthorhombic AIS NCs, were studied. The band gap values estimated from the cyclic voltammetry measurements match well with the band gap values calculated from the diffuse reflectance spectra measurements. The AIS nanostructures were found to show good electrocatalytic activity towards the hydrogen evolution reaction (HER). Our results clearly establish that the electronic and electrocatalytic properties of AIS NCs are strongly sensitive to the composition and crystal structure of AIS NCs. Monoclinic AIS was found to be the most active HER electrocatalyst, with electrocatalytic activity that is almost comparable to the MoS2 -based nanostructures reported in the literature, whereas cubic AIS was observed to be the least active of the studied crystallographic phases and compositions. In view of the HER activity and electronic band structure parameters observed herein, we hypothesize that the Fermi energy level of AIS NCs is an important factor that decides the electrocatalytic efficiency of these nanocomposites. The work presented herein, in addition to being the first of its kind regarding the composition and phase-dependence of electrochemical aspects of AIS NCs, also presents a simple solvothermal method for the synthesis of different crystallographic phases with various Ag/In molar ratios.

  10. Non-destructive measurement of carbonic anhydrase activity and the oxygen isotope composition of soil water

    NASA Astrophysics Data System (ADS)

    Jones, Sam; Sauze, Joana; Ogée, Jérôme; Wohl, Steven; Bosc, Alexandre; Wingate, Lisa

    2016-04-01

    Carbonic anhydrases are a group of metalloenzymes that catalyse the hydration of aqueous carbon dioxide (CO2). The expression of carbonic anhydrase by bacteria, archaea and eukarya has been linked to a variety of important biological processes including pH regulation, substrate supply and biomineralisation. As oxygen isotopes are exchanged between CO2 and water during hydration, the presence of carbonic anhydrase in plants and soil organisms also influences the oxygen isotope budget of atmospheric CO2. Leaf and soil water pools have distinct oxygen isotope compositions, owing to differences in pool sizes and evaporation rates, which are imparted on CO2during hydration. These differences in the isotopic signature of CO2 interacting with leaves and soil can be used to partition the contribution of photosynthesis and soil respiration to net terrestrial CO2 exchange. However, this relies on our knowledge of soil carbonic anhydrase activity and currently, the prevalence and function of these enzymes in soils is poorly understood. Isotopic approaches used to estimate soil carbonic anhydrase activity typically involve the inversion of models describing the oxygen isotope composition of CO2 fluxes to solve for the apparent, potentially catalysed, rate of oxygen exchange during hydration. This requires information about the composition of CO2 in isotopic equilibrium with soil water obtained from destructive, depth-resolved soil water sampling. This can represent a significant challenge in data collection given the considerable potential for spatial and temporal variability in the isotopic composition of soil water and limited a priori information with respect to the appropriate sampling resolution and depth. We investigated whether we could circumvent this requirement by constraining carbonic anhydrase activity and the composition of soil water in isotopic equilibrium with CO2 by solving simultaneously the mass balance for two soil CO2 steady states differing only in the

  11. Isotopic Composition of Presolar Silicon Carbide Grains Analyzed with CHILI

    NASA Astrophysics Data System (ADS)

    Stephan, T.; Trappitsch, R.; Davis, A. M.; Pellin, M. J.; Rost, D.; Savina, M. R.; Jadhav, M.; Kelly, C. H.

    2015-07-01

    Twenty-two presolar SiC grains were analyzed for Sr, Zr, and Ba isotopes with the Chicago Instrument for Laser Ionization. Most grains showed isotope patterns consistent with formation in AGB star like observed previously. One grain is a supernova grain.

  12. The effect of small scale variablity in isotopic composition of precipitation on hydrograph separation results

    NASA Astrophysics Data System (ADS)

    Fischer, Benjamin; van Meerveld, Ilja; Seibert, Jan

    2016-04-01

    Understanding runoff processes is important for predictions of streamflow quantity and quality. The two-component isotope hydrograph separation (IHS) method is a valuable tool to study how catchments transform rainfall into runoff. IHS allows the stormflow hydrograph to be separated into rainfall (event water) and water that was stored in the catchment before the event (pre-event water). To be able to perform an IHS, water samples of baseflow (pre-event water) and stormflow are collected at the stream outlet. Rainfall is usually collected at one location by hand as an event total or sampled sequentially during the event. It is usually assumed that the spatial variability in rainfall and the isotopic composition of rainfall are negligible for small (<10km2) catchments. However, different studies have shown that precipitation can vary within short distances. Subsequently it remains unclear how the spatio-temproal variability of rainfall and the stable isotope composition of rainfall affect the results of an IHS. In this study, we investigated the effects of the spatio-temporal variability in the isotopic composition of rainfall across a small headwater catchment in Switzerland. Rainfall was measured at eight locations and three streams (catchment area of 0.15, 0.23, and 0.7 km2). The isotopic composition of rainfall and streamflow were sampled for 10 different rain events (P: 5 mm intervals, Q: 12 to 51 samples per events). This dataset was used to perform a two-component isotope hydrograph separation. The results show that for some events the spatial variability in total rainfall, mean and maximum rainfall intensity and stable isotope composition of rainfall was high. There was no relation between the stable isotope composition of rainfall and the rainfall sum, rainfall intensity or altitude. The spatial variability of the isotopic composition of rainfall was for 4 out of the 10 events as large as the temporal variability in the isotopic composition. Different

  13. Elemental and iron isotopic composition of aerosols collected in a parking structure.

    PubMed

    Majestic, Brian J; Anbar, Ariel D; Herckes, Pierre

    2009-09-01

    The trace metal contents and iron isotope composition of size-resolved aerosols were determined in a parking structure in Tempe, AZ, USA. Particulate matter (PM)<2.5 microm in diameter (the fine fraction) and PM>2.5 microm were collected. Several air toxics (e.g., arsenic, cadmium, and antimony) were enriched above the crustal average, implicating automobiles as an important source. Extremely high levels of fine copper (up to 1000 ng m(-3)) were also observed in the parking garage, likely from brake wear. The iron isotope composition of the aerosols were found to be +0.15+/-0.03 per thousand and +0.18+/-0.03 per thousand for the PM<2.5 microm and PM>2.5 microm fractions, respectively. The similarity of isotope composition indicates a common source for each size fraction. To better understand the source of iron in the parking garage, the elemental composition in four brake pads (two semi-metallic and two ceramic), two tire tread samples, and two waste oil samples were determined. Striking differences in the metallic and ceramic brake pads were observed. The ceramic brake pads contained 10-20% copper by mass, while the metallic brake pads contained about 70% iron, with very little copper. Both waste oil samples contained significant amounts of calcium, phosphorous, and zinc, consistent with the composition of some engine oil additives. Differences in iron isotope composition were observed between the source materials; most notably between the tire tread (average=+0.02 per thousand) and the ceramic brake linings (average=+0.65 per thousand). Differences in isotopic composition were also observed between the metallic (average=+0.18 per thousand) and ceramic brake pads, implying that iron isotope composition may be used to resolve these sources. The iron isotope composition of the metallic brake pads was found to be identical to the aerosols, implying that brake dust is the dominant source of iron in a parking garage.

  14. Characterizing the origins of bottled water on the South Korean market using chemical and isotopic compositions.

    PubMed

    Bong, Yeon-Sik; Ryu, Jong-Sik; Lee, Kwang-Sik

    2009-01-12

    We analyzed the major elements and stable isotopes of oxygen, hydrogen, and carbon (dissolved inorganic carbon: DIC) in various types of bottled water (domestic and foreign) commercially available in South Korea to classify the water types and to identify their origins. Only marine waters and some sparkling waters could be discriminated by their physicochemical compositions. Oxygen and hydrogen isotopes made marine waters more distinguishable from other water types. The determination of the carbon isotope composition of DIC was clearly useful for distinguishing between naturally and artificially sparkling waters. In addition, statistical analysis also appeared to aid in the discrimination of bottled water types. Our results indicate that a method that combines chemical and stable isotope composition analysis with statistical analysis is the most useful for discriminating water types and characterizing the origins of bottled water.

  15. Analysis of the site-specific carbon isotope composition of propane by gas source isotope ratio mass spectrometer

    NASA Astrophysics Data System (ADS)

    Piasecki, Alison; Sessions, Alex; Lawson, Michael; Ferreira, A. A.; Neto, E. V. Santos; Eiler, John M.

    2016-09-01

    Site-specific isotope ratio measurements potentially provide valuable information about the formation and degradation of complex molecules-information that is lost in conventional bulk isotopic measurements. Here we discuss the background and possible applications of such measurements, and present a technique for studying the site-specific carbon isotope composition of propane at natural abundance based on mass spectrometric analysis of the intact propane molecule and its fragment ions. We demonstrate the feasibility of this approach through measurements of mixtures of natural propane and propane synthesized with site-specific 13C enrichment, and we document the limits of precision of our technique. We show that mass balance calculations of the bulk δ13C of propane based on our site-specific measurements is generally consistent with independent constraints on bulk δ13C. We further demonstrate the accuracy of the technique, and illustrate one of its simpler applications by documenting the site-specific carbon isotope signature associated with gas phase diffusion of propane, confirming that our measurements conform to the predictions of the kinetic theory of gases. This method can be applied to propane samples of moderate size (tens of micromoles) isolated from natural gases. Thus, it provides a means of studying the site-specific stable isotope systematics of propane at natural isotope abundances on sample sizes that are readily recovered from many natural environments. This method may also serve as a model for future techniques that apply high-resolution mass spectrometry to study the site-specific isotopic distributions of larger organic molecules, with potential applications to biosynthesis, forensics and other geochemical subjects.

  16. An assessment of upper mantle heterogeneity based on abyssal peridotite isotopic compositions

    NASA Astrophysics Data System (ADS)

    Warren, J. M.; Shimizu, N.; Sakaguchi, C.; Dick, H. J. B.; Nakamura, E.

    2009-12-01

    Abyssal peridotites, the depleted solid residues of ocean ridge melting, are the most direct samples available to assess upper oceanic mantle composition. We present detailed isotope and trace element analyses of pyroxene mineral separates from Southwest Indian Ridge abyssal peridotites and pyroxenites in order to constrain the size and length scale of mantle heterogeneity. Our results demonstrate that the mantle can be highly heterogeneous to <1 km and even <0.1 m length scales. Examination of Nd isotopes in relation to modal, trace, and major element compositions indicate that the length scales and amplitudes of heterogeneities in abyssal peridotites reflect both ancient mantle heterogeneity and recent modification by melting, melt-rock reaction and melt crystallization. The isotopic and trace element compositions of pyroxenite veins in this study indicate that they are not direct remnants of recycled oceanic crust, but instead are formed by recent melt crystallization. Combined with existing data sets, the results show that the average global isotopic composition of peridotites is similar to that of mid-ocean ridge basalts, though peridotites extend to significantly more depleted 143Nd/144Nd and 87Sr/86Sr. Standard isotope evolution models of upper mantle composition do not predict the full isotopic range observed among abyssal peridotites, as they do not account adequately for the complexities of ancient and recent melting processes.

  17. Spatial patterns of throughfall isotopic composition at the event and seasonal timescales

    NASA Astrophysics Data System (ADS)

    Allen, Scott T.; Keim, Richard F.; McDonnell, Jeffrey J.

    2015-03-01

    Spatial variability of throughfall isotopic composition in forests is indicative of complex processes occurring in the canopy and remains insufficiently understood to properly characterize precipitation inputs to the catchment water balance. Here we investigate variability of throughfall isotopic composition with the objectives: (1) to quantify the spatial variability in event-scale samples, (2) to determine if there are persistent controls over the variability and how these affect variability of seasonally accumulated throughfall, and (3) to analyze the distribution of measured throughfall isotopic composition associated with varying sampling regimes. We measured throughfall over two, three-month periods in western Oregon, USA under a Douglas-fir canopy. The mean spatial range of δ18O for each event was 1.6‰ and 1.2‰ through Fall 2009 (11 events) and Spring 2010 (7 events), respectively. However, the spatial pattern of isotopic composition was not temporally stable causing season-total throughfall to be less variable than event throughfall (1.0‰; range of cumulative δ18O for Fall 2009). Isotopic composition was not spatially autocorrelated and not explained by location relative to tree stems. Sampling error analysis for both field measurements and Monte-Carlo simulated datasets representing different sampling schemes revealed the standard deviation of differences from the true mean as high as 0.45‰ (δ18O) and 1.29‰ (d-excess). The magnitude of this isotopic variation suggests that small sample sizes are a source of substantial experimental error.

  18. Isotopic composition of Lake Agassiz-Ojibway water just prior to final drainage

    NASA Astrophysics Data System (ADS)

    Hillaire-Marcel, C.; Helie, J.; McKay, J.; Lalonde, A.

    2006-12-01

    Controversies persist with respect to the impact of the final drainage of Lake Agassiz-Ojibway on the thermohaline circulation of the North Atlantic, some 8.4 ka ago. The lack of response of planktic foraminifer isotope records, off Hudson Strait (i.e., at the outlet of the drainage channel) constitutes one of the most puzzling elements in this debate. However, data on the isotopic composition of drainage waters are needed to estimate the response of the 18-O-salinity relationship in NW Atlantic surface waters. In the literature, a large array of isotopic compositions have been suggested, notably for modeling experiment purposes. Scattered information about the isotopic composition of Lake Agassiz water does exist. It includes isotopic measurements of pore waters of lacustrine sediments [1], analyses of oxygen isotopes in cellulose from algal or plant remains [2], and stable isotope compositions of concretions from varves [3]. Whereas, relatively low oxygen isotope values (apx. -25 per mil vs. VSMOW) are inferred for Lake Agassiz waters during cold pulses of the deglaciation, most data suggest much higher values during the final stages of Lake Agassiz-Ojiway, just prior to its drainage. Calcareous concretions from Lake Ojibway varves (not necessarily contemporaneous to the lacustrine stage) yielded oxygen isotope compositions of about -10 per mil (vs. VPDB), suggesting values as high as -14 per mil (vs. VSMOW) for pore waters (assuming a 0-4 degrees C temperature range). Similar high values (as high as -8 per mil vs. VSMOW [1]) were also estimated from pore water analyses of contemporaneous Lake Agassiz sediments. Here, we used a core raised from Eastern Hudson Bay, off Great Whale River, to further document isotopic compositions of the lake waters prior to their drainage into the North Atlantic. The 7.40 m long core has an apx. 1.3 m-thick lacustrine layer at its base, including the drainage sub- layer. It is overlain by Tyrrell Sea clays. Scarce valves of Candona

  19. The Sr isotope composition of the world ocean, marginal and inland seas: Implications for the Sr isotope stratigraphy

    NASA Astrophysics Data System (ADS)

    Kuznetsov, A. B.; Semikhatov, M. A.; Gorokhov, I. M.

    2012-11-01

    We studied the Sr isotope composition of shells of modern shallow-water mollusks and coral fragments. Twenty five of the studied samples were collected in beach zones of open oceans and marginal seas; twelve and eight additional samples are from saline and freshened inland seas respectively. The 87Sr/86Sr ratio in samples from the Atlantic, Indian, and Pacific oceans and their marginal seas corresponds on average to 0.709202 ± 0.000003 and coincides with the average ratio in the standard USGS EN-1 sample. The average 87Sr/86Sr ratio in inner parts of evaporite subbasins of the Mediterranean and Red seas is identical to that of the oceanic water. In shells of shallow-water mollusks from the Black Sea and Sea of Azov, where the degree of seawater dilution by riverine runoff is as high as 50 to 70%, the 87Sr/86Sr ratio is lower than that in the oceans by only a value of 0.00002 on average. As oceanic waters penetrated into these freshwater basins no earlier than in the Holocene, we conclude that the Sr isotopic equilibration with the oceanic water is realized very rapidly in the epicontinental seas even under conditions of restricted water exchange with the World Ocean. The established uniformity of the Sr isotope composition in all geographic types of currently existing sea basins open to the World Ocean proves the efficiency of the Sr isotope stratigraphy in correlation of contemporaneous chemogenic sediments.

  20. Calcium and Oxygen Isotopic Composition of Calcium Carbonates

    NASA Astrophysics Data System (ADS)

    Niedermayr, Andrea; Eisenhauer, Anton; Böhm, Florian; Kisakürek, Basak; Balzer, Isabelle; Immenhauser, Adrian; Jürgen Köhler, Stephan; Dietzel, Martin

    2016-04-01

    Different isotopic systems are influenced in multiple ways corresponding to the crystal structure, dehydration, deprotonation, adsorption, desorption, isotope exchange and diffusion processes. In this study we investigated the structural and kinetic effects on fractionation of stable Ca- and O-isotopes during CaCO3 precipitation. Calcite, aragonite and vaterite were precipitated using the CO2 diffusion technique[1]at a constant pH of 8.3, but various temperatures (6, 10, 25 and 40° C) and precipitation rates R (101.5 to 105 μmol h-1 m-2). The calcium isotopic fractionation between solution and vaterite is lower (Δ44/40Ca= -0.10 to -0.55 ‰) compared to calcite (-0.69 to -2.04 ‰) and aragonite (-0.91 to -1.55 ‰). In contrast the fractionation of oxygen isotopes is highest for vaterite (32.1 ‰), followed by aragonite (29.2 ‰) and calcite (27.6 ‰) at 25° C and equilibrium. The enrichment of 18O vs. 16O in all polymorphs decreases with increasing precipitation rate by around -0.7 ‰ per log(R). The calcium isotopic fractionation between calcite/ vaterite and aqueous Ca2+ increases with increasing precipitation rate by ˜0.45 ‰ per log(R) and ˜0.1 ‰ per log(R) at 25° C and 40° C, respectively. In contrast the fractionation of Ca-isotopes between aragonite and aqueous Ca2+ decreases with increasing precipitation rates. The large enrichment of 18O vs. 16O isotopes in carbonates is related to the strong bond of oxygen to the small and highly charged C4+-ion. In contrast equilibrium isotopic fractionation between solution and calcite or vaterite is nearly zero as the Ca-O bond length is similar for calcite, vaterite and the hydrated Ca. Aragonite incorporates preferentially the lighter 40Ca isotope as it has very large Ca-O bonds in comparison to the hydrated Ca. At the crystal surface the lighter 40Ca isotopes are preferentially incorporated as dehydration and diffusion of lighter isotopes are faster. Consequently, the surface becomes enriched in 40

  1. Absolute quantification of Pru av 2 in sweet cherry fruit by liquid chromatography/tandem mass spectrometry with the use of a stable isotope-labelled peptide.

    PubMed

    Ippoushi, Katsunari; Sasanuma, Motoe; Oike, Hideaki; Kobori, Masuko; Maeda-Yamamoto, Mari

    2016-08-01

    Pru av 2, a pathogenesis-related (PR) protein present in the sweet cherry (Prunus avium L.) fruit, is the principal allergen of cherry and one of the chief causes of pollen food syndrome (oral allergy syndrome). In this study, a quantitative assay for this protein was developed with the use of the protein absolute quantification (AQUA) method, which consists of liquid chromatography/tandem mass spectrometry (LC/MS/MS) employing TGC[CAM]STDASGK[(13)C6,(15)N2], a stable isotope-labelled internal standard (SIIS) peptide. This assay gave a linear relationship (r(2)>0.99) in a concentration range (2.3-600fmol/μL), and the overall coefficient of variation (CV) for multiple tests was 14.6%. Thus, the contents of this allergenic protein in sweet cherry products could be determined using this assay. This assay should be valuable for allergological investigations of Pru av 2 in sweet cherry and detection of protein contamination in foods.

  2. Behaviour of Structural Carbonate Stable Carbon and Oxygen Isotope Compositions in Bioapatite During Burning of Bone

    NASA Astrophysics Data System (ADS)

    Munro, L. E.; Longstaffe, F. J.; White, C. D.

    2003-12-01

    Bioapatite, the principal inorganic phase comprising bone, commonly contains a small fraction of carbonate, which has been substituted into the phosphate structure during bone formation. The isotopic compositions of both the phosphate oxygen and the structural carbonate oxygen are now commonly used in palaeoclimatological and bioarchaeological investigations. The potential for post-mortem alteration of these isotopic compositions, therefore, is of interest, with the behaviour of structural carbonate being of most concern. In bioarchaeological studies, alteration of bone isotopic compositions has the potential to occur not only during low-temperature processes associated with burial but also during food preparation involving heating (burning, boiling). Here, we examine the stable isotopic behaviour of structural carbonate oxygen and carbon, and coexisting phosphate oxygen during the burning of bone. Freshly deceased (6<8 months) white-tailed deer leg bones (Odocoileus virginianus) were collected from Pinery Provincial Park, Ontario, Canada. Each long bone was sectioned and incrementally heated from 25 to 900° C, in 25° intervals. The samples were then ground to a standardized grain-size (45<63μ m), and changes in bioapatite crystallinity (CI) were determined using powder X-ray diffraction (pXRD), and Fourier transform infra-red spectroscopy (FTIR). Combined differential thermal and thermogravimetric analyses (DTA/TG) were used to evaluate weight loss and associated reactions during heating. Stable carbon isotope compositions of the bioapatite remain relatively constant (+/-1‰ ) during heating to 650° C. A 4‰ increase in stable carbon isotopic composition then occurs between 650-750° C, accompanied by an increase in CI, followed by a 10‰ decline at temperatures above 800° C, as carbonate carbon is lost. Carbonate and phosphate oxygen isotopic compositions are correlated over the entire heating range, with carbonate being enriched relative to phosphate by

  3. Normal variations in the isotopic composition of metabolically relevant transition metals in human blood

    NASA Astrophysics Data System (ADS)

    Van Heghe, L.; Cloquet, C.; Vanhaecke, F.

    2012-04-01

    Cu, Fe and Zn are transition metals with great catalytic, structural and regulating importance in the human body. Hence, an aberrant metabolism of these elements can have serious implications on the health of a person. It is assumed that, due to differences in isotope fractionation, the isotopic composition of these elements in whole blood of patients can be different from that in blood of healthy subjects. Therefore, isotopic analysis of the element affected by the disease can be a promising approach for early diagnosis. A method for isotopic analysis of Cu, Fe and Zn in human whole blood was developed. The simultaneous chromatographic isolation of these elements and the conditions for isotope ratio measurement via multi-collector ICP - mass spectrometry (MC-ICP-MS) were optimized. So far, only whole blood of supposedly healthy volunteers (reference population) was analyzed. Results for Fe confirmed the known differences in isotopic composition between male and female blood. It is also shown that other parameters can have influence as well, e.g., the isotopic composition of Zn seems to be governed by the diet.

  4. Spatially resolved Fe- and S-isotope composition of sedimentary pyrite

    NASA Astrophysics Data System (ADS)

    Rouxel, O.; Bekker, A.; Germain, Y.; Ponzevera, E.

    2012-04-01

    Past studies of iron and sulfur isotope records of sedimentary sulfides over geological time have placed important constraints on the biogeochemical cycle of sulfur and iron and the evolution of ocean chemistry. Since biogeochemical cycles of Fe and S are closely coupled in marine systems, Fe-limitation and S-limitation for pyrite formation in black shales should leave an imprint on the isotopic record of both elements. We developed a technique for accurate and spatially-resolved measurement of 34S/32S, 33S/32S, 56Fe/54Fe, and 57Fe/54Fe isotope ratios in sedimentary pyrite using a combination of solution and laser ablation analysis. Fe- and S-isotope ratios were measured by high-resolution MC-ICP-MS (ThermoElectron Neptune), enabling us to resolve major isobaric interferences on S isotopes and Fe isotopes from O2+, ArN+, and ArO+. A CETAC LSX 213 nm laser was used as the ablation source with He as the sample carrier gas. Fe- and S-isotope ratios were calibrated against several pyrite standards using the conventional "sample-standard bracketing technique". Instrumental mass bias of Fe and S isotopes were also corrected through an internal normalization technique using respectively Ni and Mg of known isotope composition. The long-term reproducibility of S- and Fe-isotope compositions was typically better than 0.2 per mil. We investigated the fine scale variations of d56Fe, d34S and d33S values of diagenetic pyrite nodules in several Devonian, Paleoproterozoic and Archean black shales in order to (1) explore biosignature potential of co-variations of Fe- and S-isotopes at the grain-size scale; (2) assess potential diagenetic effects on Fe-isotope fractionation during sulfide formation; and (3) assess potential mixing between isotopically distinct Fe- and S-pools using multiple S isotope data. Those results will be presented together with bulk stratigraphic S- and Fe-isotopic variations and Fe speciation data in order to establish an Fe isotope mass balance in black

  5. Changes in the South Pacific deep water Nd isotope composition over the last 140 ka

    NASA Astrophysics Data System (ADS)

    Fröllje, Henning; Basak, Chandranath; Lamy, Frank; Gersonde, Rainer; Ullermann, Johannes; Pahnke, Katharina

    2015-04-01

    The Southern Ocean plays a central role in the global overturning circulation of the ocean through the formation of intermediate and bottom waters and the import and redistribution of deep waters from all major ocean basins that make up Circumpolar Deep Water (CDW). The South Pacific is an ideal location to study the evolution of CDW over the last glacial-interglacial cycles with little direct overprint by fluctuating North Atlantic Deep Water (NADW) input. Here were present a 140ky-long record of neodymium isotope ratios (143Nd/144Nd, expressed as ɛNd) analyzed on fossil fish teeth and debris from sediment core PS75/056-1 (55° 09.74 S, 114° 47.31 W, 3581 m water depth) in the open South Pacific that is bathed today by Lower Circumpolar Deep Water (LCDW) with a small contribution from Pacific Deep Water. The Late Holocene and Marine Isotope Stage (MIS) 5 ɛNd values of -7.5 to -7.7 are close to the modern seawater isotopic composition near the core site [1]. Glacial ɛNd of about -6 is observed during MIS 2 and 6. The decrease in the ɛNd record during the penultimate deglaciation is more gradual compared to that during the last deglaciation and the most negative values of the last interglacial are reached during MIS 5c. The transition from MIS 5 into MIS 4 is characterized by a shift towards more negative ɛNd (-6.5) but full glacial values are not reached. The change to more positive ɛNd at the MIS 4/3 transition is followed by a long-term increase to maximum values reached during the last glacial maximum. The timing of the observed transitions is comparable to a nearby δ13C record (core E11-2) [2] and to published ɛNd records from the deep South Atlantic and Indian Oceans [3, 4]. We observe consistently more positive absolute ɛNd values in the South Pacific compared to the Atlantic. The offset is around one ɛNd unit during cold periods (MIS 2, 4, 6) and 1.5 ɛNd units during the interglacials. During MIS 3, on the other hand, there is little difference

  6. Trihalomethanes formed from natural organic matter isolates: Using isotopic and compositional data to help understand sources

    USGS Publications Warehouse

    Bergamaschi, B.A.; Fram, M.S.; Fujii, R.; Aiken, G.R.; Kendall, C.; Silva, S.R.

    2000-01-01

    Over 20 million people drink water from the Sacramento-San Joaquin Delta despite problematic levels of natural organic matter (NOM) and bromide in Delta water, which can form trihalomethanes (THMs) during the treatment process. It is widely believed that NOM released from Delta peat islands is a substantial contributor to the pool of THM precursors present in Delta waters. Dissolved NOM was isolated from samples collected at five channel sites within the Sacramento-San Joaquin Rivers and Delta, California, USA, and from a peat island agricultural drain. To help understand the sources of THM precursors, samples were analyzed to determine their chemical and isotopic composition, their propensity to form THMs, and the isotopic composition of the THMs. The chemical composition of the isolates was quite variable, as indicated by significant differences in carbon-13 nuclear magnetic resonance spectra and carbon-to-nitrogen concentration ratios. The lowest propensity to form THMs per unit of dissolved organic carbon was observed in the peat island agricultural drain isolate, even though it possessed the highest fraction of aromatic material and the highest specific ultraviolet absorbance. Changes in the chemical and isotopic composition of the isolates and the isotopic composition of the THMs suggest that the source of the THMs precursors was different between samples and between isolates. The pattern of variability in compositional and isotopic data for these samples was not consistent with simple mixing of river- and peat-derived organic material.

  7. Oxygen isotopic composition of relict olivine grains in cosmic spherules: Links to chondrules from carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Rudraswami, N. G.; Prasad, M. Shyam; Nagashima, K.; Jones, R. H.

    2015-09-01

    Most olivine relict grains in cosmic spherules selected for the present study are pristine and have not been disturbed during their atmospheric entry, thereby preserving their chemical, mineralogical and isotopic compositions. In order to understand the origin of the particles, oxygen isotope compositions of relict olivine grains in twelve cosmic spherules collected from deep sea sediments of the Indian Ocean were studied using secondary ion mass spectrometry. Most of the data lie close to the CCAM (Carbonaceous Chondrite Anhydrous Mineral) line, with Δ17O ranging from -5‰ to 0‰. The data overlap oxygen isotopic compositions of chondrules from carbonaceous chondrites such as CV, CK, CR and CM, which suggests that chondrules from carbonaceous chondrites are the source of relict grains in cosmic spherules. Chemical compositions of olivine in cosmic spherules are also very similar to chondrule olivine from carbonaceous chondrites. Several olivine relict grains in three cosmic spherules are 16O-rich (Δ17O -21.9‰ to -18.7‰), similar to oxygen isotopic compositions observed in calcium aluminum rich inclusions (CAIs), amoeboid olivine aggregates (AOAs), and some porphyritic chondrules from carbonaceous chondrites. These grains appear to have recorded the initial oxygen isotopic composition of the inner solar nebula. Three olivine grains from two cosmic spherules have δ18O values >+20‰, which could be interpreted as mixing with stratospheric oxygen during atmospheric entry.

  8. Genetic relations among basic lavas and ultramafic nodules: Evidence from oxygen isotope compositions

    USGS Publications Warehouse

    Kyser, T.K.; O'Neil, J.R.; Carmichael, I.S.E.

    1982-01-01

    ??18O values of unaltered basic lavas range from 4.9 to 8.3 but different types of basalts are usually restricted to narrow and distinct ranges of isotopic composition. The average ??18O values for Hawaiian tholeiites, mid-ocean ridge tholeiites, and alkali basalts are 5.4, 5.7, and 6.2 permil, respectively. Potassic lavas and andesites tend to be more 18O rich with ??18O values between 6.0 and 8.0 permil. The differences among the oxygen isotopic compositions of most of these lavas can be attributed to partial melting of isotopically distinct sources. The oxygen isotope compositions of the sources may be a function of prior melting events which produce 18O-depleted partial melts and 18O-enriched residues as a consequence of relatively large isotopic fractionations that exist at high temperatures. It is proposed that lavas with relatively low ??18O values are derived from primitive, 18O-depleted sources whereas 18O-rich basalts are produced from refractory sources that have already produced partial melts. High temperature fractionations among silicate liquids and coexisting minerals can be used in conjunction with the oxygen isotope compositions of ultramafic nodules to place constraints on the genetic relations between some nodules and different types of basic lavas. ?? 1982 Springer-Verlag.

  9. Chromium isotope composition of reducing and anoxic sediments from the Peru Margin and Cariaco Basin

    NASA Astrophysics Data System (ADS)

    Gueguen, B.; Planavsky, N.; Wang, X.; Algeo, T. J.; Peterson, L. C.; Reinhard, C. T.

    2014-12-01

    Chromium isotope systematics in marine sediments are now being used as a new redox proxy of the modern and ancient Earth's surface. Chromium is primarily delivered to the oceans by riverine inputs through weathering of Cr(III)-rich minerals present in the continental crust and oxidation of insoluble Cr(III) to soluble Cr(VI) species. Since oxidation-reduction reactions fractionate Cr isotopes whereby oxidized Cr(VI) species are preferentially enriched in heavy Cr isotopes, the Cr isotope composition of marine sediments may be useful tracers of redox conditions at the Earth's surface through geological time. Chromium is quantitatively removed in organic-rich sediments where reducing conditions prevail and promote reduction of Cr(VI) to Cr(III), and thus, these sediments should capture the ambient seawater Cr isotope composition. However, the isotopic composition of modern organic-rich sediments is poorly documented so far, and this step is essential for further modeling the global oceanic Cr isotope mass balance and assessing the effects of sedimentation and post-depositional processes on the marine Cr isotopes archive. In this study, we have characterized modern marine organic-rich sediments for their Cr isotope composition (δ53/52Cr) from two different settings, the Peru margin upwelling zone and the anoxic Cariaco Basin (Venezuela). Chromium isotopes were measured on a MC-ICP-MS (Nu Plasma) using a double-spike correction method. The authigenic fraction of shallow samples from the Peru margin sedimentary sequence with a high Total Organic Carbon (TOC) content (>10 wt%) yield an average δ53/52Crauthigenic value of +0.67 ±0.05 ‰ (2sd). However, although this value is close to the seawater value (Atlantic Ocean) and to Cariaco basin sediments (~ +0.6 ‰), reducing sediments from the Peru margin are on average isotopically slightly heavier, especially in samples having a low authigenic fraction and a low TOC content (δ53/52Crauthigenic values up to +1.30

  10. Assessment of shock effects on amphibole water contents and hydrogen isotope compositions: 1. Amphibolite experiments

    NASA Astrophysics Data System (ADS)

    Minitti, Michelle E.; Rutherford, Malcolm J.; Taylor, Bruce E.; Dyar, M. Darby; Schultz, Peter H.

    2008-02-01

    Kaersutitic amphiboles found within a subset of the Martian meteorites have low water contents and variably heavy hydrogen isotope compositions. In order to assess if impact shock-induced devolatilization and hydrogen isotope fractionation were determining factors in these water and isotopic characteristics of the Martian kaersutites, we conducted impact shock experiments on samples of Gore Mountain amphibolite in the Ames Vertical Gun Range (AVGR). A parallel shock experiment conducted on an anorthosite sample indicated that contamination of shocked samples by the AVGR hydrogen propellant was unlikely. Petrographic study of the experimental amphibolite shock products indicates that only ˜ 10% of the shock products experienced levels of damage equivalent to those found in the most highly shocked kaersutite-bearing Martian meteorites (30-35 GPa). Ion microprobe studies of highly shocked hornblende from the amphibolite exhibited elevated water contents (ΔH 2O ˜ 0.1 wt.%) and enriched hydrogen isotope compositions (Δ D ˜ + 10‰) relative to unshocked hornblende. Water and hydrogen isotope analyses of tens of milligrams of unshocked, moderately shocked, and highly shocked hornblende samples by vacuum extraction/uranium reduction and isotope ratio mass spectrometry (IRMS), respectively, are largely consistent with analyses of single grains from the ion microprobe. The mechanisms thought to have produced the excess water in most of the shocked hornblendes are shock-induced reduction of hornblende Fe and/or irreversible adsorption of hydrogen. Addition of the isotopically enriched Martian atmosphere to the Martian meteorite kaersutites via these mechanisms could explain their enriched and variable isotopic compositions. Alternatively, regrouping the water extraction and IRMS analyses on the basis of isotopic composition reveals a small, but consistent, degree of impact-induced devolatilization (˜ 0.1 wt.% H 2O) and H isotope enrichment (Δ D ˜ + 10

  11. Natural variations in calcium isotope composition as a monitor of bone mineral balance in humans.

    NASA Astrophysics Data System (ADS)

    Skulan, J.; Anbar, A.; Thomas, B.; Smith, S.

    2004-12-01

    The skeleton is the largest reservoir of calcium in the human body and is responsible for the short term control of blood levels of this element. Accurate measurement of changes in bone calcium balance is critical to understanding how calcium metabolism responds to physiological and environmental changes and, more specifically, to diagnosing and evaluating the effectiveness of treatments for osteoporosis and other serious calcium-related disorders. It is very difficult to measure bone calcium balance using current techniques, however, because these techniques rely either on separate estimates of bone resorption and formation that are not quantitatively comparable, or on complex and expensive studies of calcium kinetics using administered isotopic tracers. This difficulty is even more apparent and more severe for measurements of short-term changes in bone calcium balance that do not produce detectable changes in bone mineral density. Calcium isotopes may provide a novel means of addressing this problem. The foundation of this isotope application is the ca. 1.3 per mil fractionation of calcium during bone formation, favoring light calcium in the bone. This fractionation results in a steady-state isotopic offset between calcium in bone and calcium in soft tissues, blood and urine. Perturbations to this steady state due to changes in the net formation or resorption of bone should be reflected in changes in the isotopic composition of soft tissues and fluids. Here we present evidence that easily detectable shifts in the natural calcium isotope composition of human urine rapidly reflect changes in bone calcium balance. Urine from subjects in a 17-week bed rest study was analyzed for calcium isotopic composition. Bed rest promotes net resorption of bone, shifting calcium from bone to soft tissues, blood and urine. The calcium isotope composition of patients in this study shifted toward lighter values during bed rest, consistent with net resorption of isotopically

  12. The stable hydrogen isotopic composition of sedimentary plant waxes as quantitative proxy for rainfall in the West African Sahel

    NASA Astrophysics Data System (ADS)

    Niedermeyer, Eva M.; Forrest, Matthew; Beckmann, Britta; Sessions, Alex L.; Mulch, Andreas; Schefuß, Enno

    2016-07-01

    Various studies have demonstrated that the stable hydrogen isotopic composition (δD) of terrestrial leaf waxes tracks that of precipitation (δDprecip) both spatially across climate gradients and over a range of different timescales. Yet, reconstructed estimates of δDprecip and corresponding rainfall typically remain largely qualitative, due mainly to uncertainties in plant ecosystem net fractionation, relative humidity, and the stability of the amount effect through time. Here we present δD values of the C31n-alkane (δDwax) from a marine sediment core offshore the Northwest (NW) African Sahel covering the past 100 years and overlapping with the instrumental record of rainfall. We use this record to investigate whether accurate, quantitative estimates of past rainfall can be derived from our δDwax time series. We infer the composition of vegetation (C3/C4) within the continental catchment area by analysis of the stable carbon isotopic composition of the same compounds (δ13Cwax), calculated a net ecosystem fractionation factor, and corrected the δDwax time series accordingly to derive δDprecip. Using the present-day relationship between δDprecip and the amount of precipitation in the tropics, we derive quantitative estimates of past precipitation amounts. Our data show that (a) vegetation composition can be inferred from δ13Cwax, (b) the calculated net ecosystem fractionation represents a reasonable estimate, and (c) estimated total amounts of rainfall based on δDwax correspond to instrumental records of rainfall. Our study has important implications for future studies aiming to reconstruct rainfall based on δDwax; the combined data presented here demonstrate that it is feasible to infer absolute rainfall amounts from sedimentary δDwax in tandem with δ13Cwax in specific depositional settings.

  13. Transition of the Isotopic Composition of Leaf Water to the Isotopic Steady State in Soybean and Corn

    NASA Astrophysics Data System (ADS)

    Kim, K.; Lee, X.; Welp, L. R.

    2007-12-01

    The isotope composition of leaf water (δL) plays an important role in the isotopic water and carbon fluxes between terrestrial plants and the atmosphere. The objective of this study is to improve our understanding of environmental and biological controls on the transition of δL to steady state through laboratory experiments. Plants (soybean, Glycine max; corn, Zea mays) were grown hydroponically with water of a known isotopic content in a greenhouse. On the day of the experiment, they were first moved to ambient environment in full sunlight for at least 6 hr and then into a dark container inside the lab for up to 48 hr in which water vapor isotope ratios, temperature, and humidity were controlled. This arrangement created a step change in the forcing on the plant isotopic exchange. Leaves were sampled prior to the transfer to the dark container and 6 more times every 4 - 12 hr over the experiment. In the first set of experiments, humidity inside the container was saturated to mimic dew events in field conditions. In the second set, humidity was controlled at approximately 95%. Water from the leaf samples was extracted by a vacuum line and was analyzed for both δD and δ18O. The dataset will allow us to evaluate leaf water isotopic theories by exploring the transitions of δL in response to the step change. Specifically, we are interested in whether the stomatal opening is an effective pathway for gaseous exchange in total darkness and how the transitional behaviors of δL differ between the C3 and C4 photosynthesis pathways.

  14. Ultra-depleted isotopic compositions in fertile asthenosphere-derived peridotites: constraints on the composition of the upper mantle

    NASA Astrophysics Data System (ADS)

    Byerly, B. L.; Lassiter, J. C.

    2012-12-01

    Recent studies of abyssal peridotites (AP) and OIB xenoliths have reported refractory, isotopically ultra-depleted domains within the convecting upper mantle with Nd- and Hf-isotope compositions that extend far beyond the MORB field. These results have important implications regarding the average composition of the depleted upper mantle and the genetic relationship between MORB and AP. However, the abundance of ultra-depleted domains in the mantle is unclear. In addition, recent melt extraction processes at mid-ocean ridges make it difficult to evaluate the compositions of ultra-depleted domains prior to exhumation and thus evaluate their role in melt generation. To better constrain the abundance and composition of typical convecting upper mantle, we examined a suite of spinel peridotite xenoliths from the central Rio Grande Rift (RGR) where most of the preexisting lithosphere has been convectively removed and replaced with depleted upper mantle. Seismic tomography indicates that the lithosphere beneath the RGR has been substantially removed (Gao, 2004), and geochemical evidence supports this. Two distinct populations of xenoliths are observed from Elephant Butte, central RGR. One population, interpreted to derive from residual Proterozoic lithospheric mantle, is refractory (bulk Al2O3 <2.3 wt.%), LREE- and LILE-enriched, has enriched Sr, Nd, and Pb isotopic compositions and along with xenoliths from the Eastern Colorado Plateau define a strong Lu/Hf-176Hf/177Hf "pseudo-isochron" with an apparent age of ~1.6 Ga. In contrast, the majority of the RGR xenoliths have fertile major element compositions (bulk Al2O3 ~ 4.0 wt %), low spinel Cr# (~10), and LREE-depleted trace element patterns, and overlap with composition estimates for the depleted mantle (Workman & Hart, 2005). We interpret these xenoliths to reflect recent replacement of the pre-existing lithosphere with material from the convecting upper mantle. The fertile xenoliths have cpx Sr-, Nd-, and Hf-isotope

  15. Oxygen isotope composition as a tracer for the origins of rubies and sapphires

    NASA Astrophysics Data System (ADS)

    Giuliani, Gaston; Fallick, Anthony E.; Garnier, Virginie; France-Lanord, Christian; Ohnenstetter, Daniel; Schwarz, Dietmar

    2005-04-01

    Oxygen isotopic compositions of rubies and sapphires from 106 deposits worldwide, as well as heated natural corundum, have been measured in this study. Artificially heated corundums have the same oxygen isotopic composition as unheated material. The 18O/16O ratio of natural corundum is a good indicator of its geological environment of formation. The consistently restricted δ18O range found for each type of deposit is explained by host-rock buffering during fluid-rock interaction. The δ18O constrains the geological source of the major type of gem-quality rubies sold on the market and brings new insight to gems found in placers. High-quality blue sapphires from Kashmir, Andranondambo, and Sri Lanka have specific oxygen isotopic ranges, but they overlap those of Mogok in Myanmar. Combined with traditional gemology techniques, oxygen isotope analysis will contribute toward defining the origin of some commercial high-value blue sapphires, especially from Kashmir.

  16. Ca-,Al-rich inclusions in the unique chondrite ALH85085 - Petrology, chemistry, and isotopic compositions

    NASA Astrophysics Data System (ADS)

    Kimura, M.; El Goresy, A.; Palme, H.; Zinner, E.

    1993-05-01

    A comprehensive study is performed for the Ca-,Al-rich inclusions (CAIs) in the unique chondrite ALH85085. The ALH85085 inclusions are smaller (5-80 microns) and more refractory than their counterparts in carbonaceous chondrites. The study includes 42 inclusions for petrography and mineralogy, 15 for bulk major and minor element chemical composition, six for Mg-Al isotopic systematics, 10 for Ca isotopes, nine for Ti isotopes, and six for trace element abundances. In addition, oxygen-isotopic compositions were determined in minerals from a single inclusion. No correlation is found between mineralogy, major element chemistry, and trace element abundances. It is further shown that the high-temperature geochemical behavior of ultrarefractory trace elements is decoupled from that of the major elements Ca and Ti (Ti is correlated with the relatively volatile elements Nb and Yb) implying that perovskite is of only minor importance as carrier of ultrarefractories.

  17. Natural variations in the rhenium isotopic composition of meteorites

    NASA Astrophysics Data System (ADS)

    Liu, R.; Hu, L.; Humayun, M.

    2017-03-01

    Rhenium is an important element with which to test hypotheses of isotope variation. Historically, it has been difficult to precisely correct the instrumental mass bias in thermal ionization mass spectrometry. We used W as an internal standard to correct mass bias on the MC-ICP-MS, and obtained the first precise δ187Re values ( ±0.02‰, 2SE) for iron meteorites and chondritic metal. Relative to metal from H chondrites, IVB irons are systematically higher in δ187Re by 0.14 ‰. δ187Re for other irons are similar to H chondritic metal, although some individual samples show significant isotope fractionation. Since 185Re has a high neutron capture cross section, the effect of galactic cosmic-ray (GCR) irradiation on δ187Re was examined using correlations with Pt isotopes. The pre-GCR irradiation δ187Re for IVB irons is lower, but the difference in δ187Re between IVB irons and other meteoritic metal remains. Nuclear volume-dependent fractionation for Re is about the right magnitude near the melting point of iron, but because of the refractory and compatible character of Re, a compelling explanation in terms of mass-dependent fractionation is elusive. The magnitude of a nucleosynthetic s-process deficit for Re estimated from Mo and Ru isotopes is essentially unresolvable. Since thermal processing reduced nucleosynthetic effects in Pd, it is conceivable that Re isotopic variations larger than those in Mo and Ru may be present in IVBs since Re is more refractory than Mo and Ru. Thus, the Re isotopic difference between IVBs and other irons or chondritic metal remains unexplained.

  18. Clumped Isotope Composition of Cold-Water Corals: A Role for Vital Effects?

    NASA Astrophysics Data System (ADS)

    Spooner, P.; Guo, W.; Robinson, L. F.

    2014-12-01

    Measurements on a set of cold-water corals (mainly Desmophyllum dianthus) have suggested that their clumped isotope composition could serve as a promising proxy for reconstructing paleocean temperatures. Such measurements have also offered support for certain isotope models of coral calcification. However, there are differences in the clumped isotope compositions between warm-water and cold-water corals, suggesting that different kinds of corals could have differences in their biocalcification processes. In order to understand the systematics of clumped isotope variations in cold-water corals more fully, we present clumped isotope data from a range of cold-water coral species from the tropical Atlantic and the Southern Ocean.Our samples were either collected live or recently dead (14C ages < 1,000 yrs) with associated temperature data. They include a total of 11 solitary corals and 1 colonial coral from the Atlantic, and 8 solitary corals from the Southern Ocean. The data indicate that coral clumped isotope systematics may be more complicated than previously thought. For example, for the genus Caryophyllia we observe significant variations in clumped isotope compositions for corals which grew at the same temperature with an apparent negative correlation between Δ47 and δ18O, different to patterns previously observed in Desmophyllum. These results indicate that existing isotope models of biocalcification may not apply equally well to all corals. Clumped isotope vital effects may be present in certain cold-water corals as they are in warm-water corals, complicating the use of this paleoclimate proxy.

  19. The GENESIS Mission: Solar Wind Isotopic and Elemental Compositions and Their Implications

    NASA Astrophysics Data System (ADS)

    Wiens, R. C.; Burnett, D. S.; McKeegan, K. D.; Kallio, A. P.; Mao, P. H.; Heber, V. S.; Wieler, R.; Meshik, A.; Hohenberg, C. M.; Mabry, J. C.; Gilmour, J.; Crowther, S. A.; Reisenfeld, D. B.; Jurewicz, A.; Marty, B.; Pepin, R. O.; Barraclough, B. L.; Nordholt, J. E.; Olinger, C. T.; Steinberg, J. T.

    2008-12-01

    The GENESIS mission was a novel NASA experiment to collect solar wind at the Earth's L1 point for two years and return it for analysis. The capsule crashed upon re-entry in 2004, but many of the solar-wind collectors were recovered, including separate samples of coronal hole, interstream, and CME material. Laboratory analyses of these materials have allowed higher isotopic precision than possible with current in-situ detectors. To date GENESIS results have been obtained on isotopes of O, He, Ne, Ar, Kr, and Xe on the order of 1% accuracy and precision, with poorer uncertainty on Xe isotopes and significantly better uncertainties on the lighter noble gases. Elemental abundances are available for the above elements as well as Mg, Si, and Fe. When elemental abundances are compared with other in situ solar wind measurements, agreement is generally quite good. One exception is the Ne elemental abundance, which agrees with Ulysses and Apollo SWC results, but not with ACE. Neon is of particular interest because of the uncertainty in the solar Ne abundance, which has significant implications for the standard solar model. Helium isotopic results of material from the different solar wind regimes collected by GENESIS is consistent with isotopic fractionation predictions of the Coulomb drag model, suggesting that isotopic fractionation corrections need to be applied to heavier elements as well when extrapolating solar wind to solar compositions. Noble gas isotopic compositions from GENESIS are consistent with those obtained for solar wind trapped in lunar grains, but have for the first time yielded a very precise Ar isotopic result. Most interesting for cosmochemistry is a preliminary oxygen isotopic result from GENESIS which indicates a solar enrichment of ~4% in 16O relative to the planets, consistent with a photolytic self-shielding phenomenon during solar system formation. Analyses of solar wind N and C isotopes may further elucidate this phenomenon. Preliminary results

  20. Variation in the terrestrial isotopic composition and atomic weight of argon

    USGS Publications Warehouse

    Böhlke, John Karl

    2014-01-01

    The isotopic composition and atomic weight of argon (Ar) are variable in terrestrial materials. Those variations are a source of uncertainty in the assignment of standard properties for Ar, but they provide useful information in many areas of science. Variations in the stable isotopic composition and atomic weight of Ar are caused by several different processes, including (1) isotope production from other elements by radioactive decay (radiogenic isotopes) or other nuclear transformations (e.g., nucleogenic isotopes), and (2) isotopic fractionation by physical-chemical processes such as diffusion or phase equilibria. Physical-chemical processes cause correlated mass-dependent variations in the Ar isotope-amount ratios (40Ar/36Ar, 38Ar/36Ar), whereas nuclear transformation processes cause non-mass-dependent variations. While atmospheric Ar can serve as an abundant and homogeneous isotopic reference, deviations from the atmospheric isotopic ratios in other Ar occurrences limit the precision with which a standard atomic weight can be given for Ar. Published data indicate variation of Ar atomic weights in normal terrestrial materials between about 39.7931 and 39.9624. The upper bound of this interval is given by the atomic mass of 40Ar, as some samples contain almost pure radiogenic 40Ar. The lower bound is derived from analyses of pitchblende (uranium mineral) containing large amounts of nucleogenic 36Ar and 38Ar. Within this interval, measurements of different isotope ratios (40Ar/36Ar or 38Ar/36Ar) at various levels of precision are widely used for studies in geochronology, water–rock interaction, atmospheric evolution, and other fields.

  1. Clumped isotope composition of cold-water corals: A role for vital effects?

    NASA Astrophysics Data System (ADS)

    Spooner, Peter T.; Guo, Weifu; Robinson, Laura F.; Thiagarajan, Nivedita; Hendry, Katharine R.; Rosenheim, Brad E.; Leng, Melanie J.

    2016-04-01

    The carbonate clumped isotope thermometer is a promising tool for determining past ocean temperatures. It is based on the temperature dependence of rare isotopes 'clumping' into the same carbonate ion group in the carbonate mineral lattice. The extent of this clumping effect is independent of the isotope composition of the water from which carbonate precipitates, providing unique advantages over many other paleotemperature proxies. Existing calibrations of this thermometer in cold-water and warm-water corals suggest clumped isotope 'vital effects' are negligible in cold-water corals but may be significant in warm-water corals. Here, we test the calibration of the carbonate clumped isotope thermometer in cold-water corals with a recently collected and well characterised sample set spanning a range of coral genera (Balanophyllia, Caryophyllia, Dasmosmilia, Desmophyllum, Enallopsammia and Javania). The clumped isotope compositions (Δ47) of these corals exhibit systematic dependences on their growth temperatures, confirming the basis of the carbonate clumped isotope thermometer. However, some cold-water coral genera show Δ47 values that are higher than the expected equilibrium values by up to 0.05‰ (equivalent to underestimating temperature by ∼9 °C) similar to previous findings for some warm-water corals. This finding suggests that the vital effects affecting corals Δ47 are common to both warm- and cold-water corals. By comparison with models of the coral calcification process we suggest that the clumped isotope offsets in these genera are related to the kinetic isotope effects associated with CO2 hydration/hydroxylation reactions in the corals' calcifying fluid. Our findings complicate the use of the carbonate clumped isotope thermometer in corals, but suggest that species- or genus-specific calibrations could be useful for the future application of this paleotemperature proxy.

  2. MAST - A mass spectrometer telescope for studies of the isotopic composition of solar, anomalous, and galactic cosmic ray nuclei

    NASA Technical Reports Server (NTRS)

    Cook, Walter R.; Cummings, Alan C.; Cummings, Jay R.; Garrard, Thomas L.; Kecman, Branislav; Mewaldt, Richard A.; Selesnick, Richard S.; Stone, Edward C.; Von Rosenvinge, T. T.

    1993-01-01

    The Mass Spectrometer Telescope (MAST) on SAMPEX is designed to provide high resolution measurements of the isotopic composition of energetic nuclei from He to Ni (Z = 2 to 28) over the energy range from about 10 to several hundred MeV/nuc. During large solar flares MAST will measure the isotopic abundances of solar energetic particles to determine directly the composition of the solar corona, while during solar quiet times MAST will study the isotopic composition of galactic cosmic rays. In addition, MAST will measure the isotopic composition of both interplanetary and trapped fluxes of anomalous cosmic rays, believed to be a sample of the nearby interstellar medium.

  3. Factors that control the stable carbon isotopic composition of methane produced in an anoxic marine sediment

    NASA Astrophysics Data System (ADS)

    Alperin, M. J.; Blair, N. E.; Albert, D. B.; Hoehler, T. M.; Martens, C. S.

    1992-09-01

    The carbon isotopic composition of methane produced in anoxic marine sediment is controlled by four factors: (1) the pathway of methane formation, (2) the isotopic composition of the methanogenic precursors, (3) the isotope fractionation factors for methane production, and (4) the isotope fractionation associated with methane oxidation. The importance of each factor was evaluated by monitoring stable carbon isotope ratios in methane produced by a sediment microcosm. Methane did not accumulate during the initial 42-day period when sediment contained sulfate, indicating little methane production from "noncompetitive" substrates. Following sulfate depletion, methane accumulation proceeded in three distinct phases. First, CO2 reduction was the dominant methanogenic pathway and the isotopic composition of the methane produced ranged from -80 to -94‰. The acetate concentration increased during this phase, suggesting that acetoclastic methanogenic bacteria were unable to keep pace with acetate production. Second, acetate fermentation became the dominant methanogenic pathway as bacteria responded to elevated acetate concentrations. The methane produced during this phase was progressively enriched in 13C, reaching a maximum δ13C value of -42‰. Third, the acetate pool experienced a precipitous decline from >5 mM to <20 μM and methane production was again dominated by CO2 reduction. The δ13C of methane produced during this final phase ranged from -46 to -58‰. Methane oxidation concurrent with methane production was detected throughout the period of methane accumulation, at rates equivalent to 1 to 8% of the gross methane production rate. Thus methane oxidation was too slow to have significantly modified the isotopic signature of methane. A comparison of microcosm and field data suggests that similar microbial interactions may control seasonal variability in the isotopic composition of methane emitted from undisturbed Cape Lookout Bight sediment.

  4. Factors that control the stable carbon isotopic composition of methane produced in an anoxic marine sediment

    NASA Technical Reports Server (NTRS)

    Alperin, M. J.; Blair, Neal E.; Albert, D. B.; Hoehler, T. M.; Martens, C. S.

    1993-01-01

    The carbon isotopic composition of methane produced in anoxic marine sediment is controlled by four factors: (1) the pathway of methane formation, (2) the isotopic composition of the methanogenic precursors, (3) the isotope fractionation factors for methane production, and (4) the isotope fractionation associated with methane oxidation. The importance of each factor was evaluated by monitoring stable carbon isotope ratios in methane produced by a sediment microcosm. Methane did not accumulate during the initial 42-day period when sediment contained sulfate, indicating little methane production from 'noncompetitive' substrates. Following sulfate depletion, methane accumulation proceeded in three distinct phases. First, CO2 reduction was the dominant methanogenic pathway and the isotopic composition of the methane produced ranged from -80 to -94 per thousand. The acetate concentration increased during this phase, suggesting that acetoclastic methanogenic bacteria were unable to keep pace with acetate production. Second, acetate fermentation became the dominant methanogenic pathway as bacteria responded to elevated acetate concentrations. The methane produced during this phase was progressively enriched in C-13, reaching a maximum delta(C-13) value of -42 per thousand. Third, the acetate pool experienced a precipitous decline from greater than 5 mM to less than 20 micro-M and methane production was again dominated by CO2 reduction. The delta(C-13) of methane produced during this final phase ranged from -46 to -58 per thousand. Methane oxidation concurrent with methane production was detected throughout the period of methane accumulation, at rates equivalent to 1 to 8 percent of the gross methane production rate. Thus methane oxidation was too slow to have significantly modified the isotopic signature of methane. A comparison of microcosm and field data suggests that similar microbial interactions may control seasonal variability in the isotopic composition of methane

  5. Potassium Isotopic Compositions of NIST Potassium Standards and 40Ar/39Ar Mineral Standards

    NASA Technical Reports Server (NTRS)

    Morgan, Leah; Tappa, Mike; Ellam, Rob; Mark, Darren; Higgins, John; Simon, Justin I.

    2013-01-01

    Knowledge of the isotopic ratios of standards, spikes, and reference materials is fundamental to the accuracy of many geochronological methods. For example, the 238U/235U ratio relevant to U-Pb geochronology was recently re-determined [1] and shown to differ significantly from the previously accepted value employed during age determinations. These underlying values are fundamental to accurate age calculations in many isotopic systems, and uncertainty in these values can represent a significant (and often unrecognized) portion of the uncertainty budget for determined ages. The potassium isotopic composition of mineral standards, or neutron flux monitors, is a critical, but often overlooked component in the calculation of K-Ar and 40Ar/39Ar ages. It is currently assumed that all terrestrial materials have abundances indistinguishable from that of NIST SRM 985 [2]; this is apparently a reasonable assumption at the 0.25per mille level (1s) [3]. The 40Ar/39Ar method further relies on the assumption that standards and samples (including primary and secondary standards) have indistinguishable 40K/39K values. We will present data establishing the potassium isotopic compositions of NIST isotopic K SRM 985, elemental K SRM 999b, and 40Ar/39Ar biotite mineral standard GA1550 (sample MD-2). Stable isotopic compositions (41K/39K) were measured by the peak shoulder method with high resolution MC-ICP-MS (Thermo Scientific NEPTUNE Plus), using the accepted value of NIST isotopic SRM 985 [2] for fractionation [4] corrections [5]. 40K abundances were measured by TIMS (Thermo Scientific TRITON), using 41K/39K values from ICP-MS measurements (or, for SRM 985, values from [2]) for internal fractionation corrections. Collectively these data represent an important step towards a metrologically traceable calibration of 40K concentrations in primary 40Ar/39Ar mineral standards and improve uncertainties by ca. an order of magnitude in the potassium isotopic compositions of standards.

  6. The effect of soil hydrology on the oxygen and hydrogen isotopic compositions of plants' source water

    NASA Astrophysics Data System (ADS)

    Tang, Kuilian; Feng, Xiahong

    2001-02-01

    Many studies have demonstrated that the isotopic composition of plants' source water is the main factor affecting the isotopic composition of tree rings. Because of soil hydrological processes, soil water as the source water for plants may isotopically differ from precipitation that contains climatic information (such as surface temperature). This study addresses the effects of soil hydrological processes on the isotopic compositions of soil water and discusses how these effects affect interpretations of tree ring data in isotopic dendroclimatology. We collected precipitation, soil gas at two depths (20 and 50 cm), and twigs from a maple tree ( Acer saccharum) on a biweekly basis during the growing season in 1997-1999 at Hanover, NH, USA. Water was extracted from the twig samples by vacuum distillation. All water samples were analyzed for both δD and δ 18O. Soil CO 2 was extracted from soil gas and measured for the δ 18O values, and using the soil temperature and assuming isotopic equilibrium between CO 2 and H 2O, we calculated the δ 18O values of soil water. Comparisons among the isotopic time series of each type of sample indicate the following. (1) The isotopic composition of soil water is much less variable than that of precipitation, suggesting isotopic mixing between waters of different precipitation events. (2) In early spring, soil water at all depths is isotopically similar to winter precipitation, but with time the surface soil water becomes progressively enriched in deuterium and 18O due to infiltration of summer rain and enrichment through soil water evaporation. (3) The influence of summer precipitation decreases with increasing depth, and soil at 50 cm can only receive water from large storms. (4) Replacement of old soil water with new infiltrating water is dependent upon frequency and intensity of growing season precipitation, and it is generally more efficient in a wet year than in a dry year. (5) The tree we studied uses water mainly from near

  7. Carbon isotopic composition of graphite grains in the EL Taco IAB iron meteorite

    NASA Astrophysics Data System (ADS)

    Zipfel, J.; Hutcheon, I. D.; Marti, K.

    1997-03-01

    Carbon isotopes have been analyzed in individual graphite grains of the El Taco iron meteorite. Graphite is present in four distinct petrographic associations and a total of 28 grains has been analyzed from all areas. The C isotopic composition varies from delta-C-13 = +4 to -29 percent and exhibits well-defined correlations with graphite morphology. The El Taco graphites contain much less N, with CN/C ratios of 0.0027 to 0.005, than graphites from Acapulco or unequilibrated ordinary chondrites. Graphite appears to retain an isotopic record of precursor materials despite high peak temperatures and may be an important tracer of early solar system proceses.

  8. Zirconium isotope constraints on the composition of Theia and current Moon-forming theories

    NASA Astrophysics Data System (ADS)

    Akram, W.; Schönbächler, M.

    2016-09-01

    The giant impact theory is the most widely recognized formation scenario of the Earth's Moon. Giant impact models based on dynamical simulations predict that the Moon acquired a significant amount of impactor (Theia) material, which is challenging to reconcile with geochemical data for O, Si, Cr, Ti and W isotopes in the Earth and Moon. Three new giant impact scenarios have been proposed to account for this discrepancy - hit-and-run impact, impact with a fast-spinning protoEarth and massive impactors - each one reducing the proportion of the impactor in the Moon compared to the original canonical giant impact model. The validity of each theory and their different dynamical varieties are evaluated here using an integrated approach that considers new high-precision Zr isotope measurements of lunar rocks, and quantitative geochemical modelling of the isotopic composition of the impactor Theia. All analysed lunar samples (whole-rock, ilmenite and pyroxene separates) display identical Zr isotope compositions to that of the Earth within the uncertainty of 13 ppm for 96Zr/90Zr (2σ weighted average). This 13 ppm upper limit is used to infer the most extreme isotopic composition that Theia could have possessed, relative to the Earth, for each of the proposed giant impact theories. The calculated Theian composition is compared with the Zr isotope compositions of different solar system materials in order to constrain the source region of the impactor. As a first order approximation, we show that all considered models (including the canonical) are plausible, alleviating the initial requirement for the new giant impact models. Albeit, the canonical and hit-and-run models are the most restrictive, suggesting that the impactor originated from a region close to the Earth. The fast-spinning protoEarth and massive impactor models are more relaxed and increase the allowed impactor distance from the Earth. Similar calculations carried out for O, Cr, Ti and Si isotope data support

  9. Xenon isotopic composition of the Mid Ocean Ridge Basalt (MORB) source

    NASA Astrophysics Data System (ADS)

    Peto, M. K.; Mukhopadhyay, S.

    2012-12-01

    Although convection models do not preclude preservation of smaller mantle regions with more pristine composition throughout Earth's history, it has been widely assumed that the moon forming giant impact likely homogenizes the whole mantle following a magma ocean that extended all the way to the bottom of the mantle. Recent findings of tungsten and xenon heterogeneities in the mantle [1,2,3,4], however, imply that i) the moon forming giant impact may not have homogenized the whole mantle and ii) plate tectonics was inefficient in erasing early formed compositional differences, particularly for the xenon isotopes. Therefore, the xenon isotope composition in the present day mantle still preserves a memory of early Earth processes. However, determination of the xenon isotopic composition of the mantle source is still scarce, since the mantle composition is overprinted by post-eruptive atmospheric contamination in basalts erupted at ocean islands and mid ocean ridges. The xenon composition of the depleted upper mantle has been defined by the gas rich sample, 2πD43 (also known as "popping rock"), from the North Atlantic (13° 469`N). However, the composition of a single sample is not likely to define the composition of the upper mantle, especially since popping rock has an "enriched" trace element composition. We will present Ne, Ar and Xe isotope data on MORB glass samples with "normal" helium isotope composition (8±1 Ra) from the Southeast Indian Ridge, the South Atlantic Ridge, the Sojourn Ridge, the Juan de Fuca, the East Pacific Rise, and the Gakkel Ridge. Following the approach of [1], we correct for syn- and post-eruptive atmosphere contamination, and determine the variation of Ar and Xe isotope composition of the "normal" MORB source. We investigate the effect of atmospheric recycling in the variation of MORB mantle 40Ar/36Ar and 129Xe/130Xe ratios, and attempt to constrain the average upper mantle argon and xenon isotopic compositions. [1] Mukhopadhyay, Nature

  10. The riverine silicon isotope composition of the Amazon Basin

    NASA Astrophysics Data System (ADS)

    Hughes, H. J.; Sondag, F.; Santos, R. V.; André, L.; Cardinal, D.

    2013-11-01

    We present here the first large-scale study of riverine silicon isotope signatures in the Amazon Basin. The Amazon and five of its main tributaries were studied at different seasons of the annual hydrological cycle. The δ30Si signature of the dissolved silicon (DSi) exported to the estuary (weighted for DSi flux) for the period considered is estimated at +0.92‰. A river cross-section shows the homogeneity of the Amazon River regarding DSi concentration and isotope ratio. The biogenic silica (BSi) concentration measured in surface water from all rivers is generally small compared to the DSi reservoir but large variations exist between rivers. Very low isotope signatures were measured in the upper Rio Negro (δ30Si = +0.05 ± 0.06‰), which we explain both by an equilibrium between clay formation and dissolution and by gibbsite formation. The Si isotope fractionation in the Andean tributaries and the Amazon main stem can be explained by clay formation and follow either a Rayleigh or a batch equilibrium fractionation model. Our results also suggest that the formation of 2:1 clays induces a fractionation factor similar to that of kaolinite formation.

  11. Determining the oxygen isotope composition of evapotranspiration with eddy covariance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The oxygen isotope componsition of evapotranspiration (dF) represents an important tracer in the study of biosphere-atmosphere interactions, hydrology, paleoclimate, and carbon cycling. Here we demonstrate direct measurement of dF based on eddy covariance (EC) and tunable diode laser (EC-TDL) techni...

  12. Natural gas constituent and carbon isotopic composition in petroliferous basins, China

    NASA Astrophysics Data System (ADS)

    Zhu, Guangyou; Wang, Zhengjun; Dai, Jinxing; Su, Jing

    2014-02-01

    There are abundant gas resources in petroliferous basins of China. Large to midsize gas fields are found in Eastern, central and Western of China. However, origin, constituents and isotopic composition of natural gas in different gas fields are varied distinctly, and some present strong chemical secondary alteration and show variation both in age and space. Based on the systematic analysis of constituents and carbon isotope of a large number of gas samples, combined with the geological characteristics, this paper classifies the origins of the gases, explores the gas isotope characteristics and evolutionary regulation with the variation time and space, and further discusses the distinctive geochemistry of the gases in China. These gases are dominated by dry gas, its methane carbon isotope values range from -10‰ to -70‰, ethane from -16‰ to -52‰, propane from -13‰ to -43‰, and butane from -18‰ to -34‰. The carbon isotopes of most gases show the characteristics of humic-derived gas and crude oil cracked gas. In addition, large primary biogenic gas fields have been discovered in the Qaidam basin; inorganic-derived alkane gases have been discovered in deep of the Songliao Basin. Half of these gas fields are characterized by the alkane carbon isotope reversal in different degrees. Research indicates there are several reasons can result in carbon isotope reversal. Firstly, gas charge of different genetic types or different source in one gas reservoir may cause carbon isotope reversal. Besides, high-over mature evolution of gas can also lead to the carbon isotopic reversal of alkanes. Thirdly, secondary alteration of hydrocarbons may also result in abnormal distribution of carbon isotope, isotope transforms to unusual light and heavy.

  13. Zinc isotope fractionation during mantle melting and constraints on the Zn isotope composition of Earth's upper mantle

    NASA Astrophysics Data System (ADS)

    Wang, Ze-Zhou; Liu, Sheng-Ao; Liu, Jingao; Huang, Jian; Xiao, Yan; Chu, Zhu-Yin; Zhao, Xin-Miao; Tang, Limei

    2017-02-01

    compositions of MORB. Therefore, preferential melting of spinel in the peridotites may account for the Zn isotopic difference between spinel peridotites and basalts. By contrast, the absence of Zn isotope fractionation between silicate minerals suggests that Zn isotopes are not significantly fractionated during partial melting of spinel-free garnet-facies mantle. If the studied non-metasomatized peridotites represent the refractory upper mantle, mass balance calculation shows that the depleted MORB mantle (DMM) has a δ66Zn value of +0.20 ± 0.05‰ (2SD), which is lighter than the primitive upper mantle (PUM) estimated in previous studies (+0.28 ± 0.05‰, 2SD, Chen et al., 2013b; +0.30 ± 0.07‰, 2SD, Doucet et al., 2016). This indicates that the Earth's upper mantle has a heterogeneous Zn isotopic composition vertically, which is probably due to shallow mantle melting processes.

  14. The oxygen isotopic composition of the Sun inferred from captured solar wind.

    PubMed

    McKeegan, K D; Kallio, A P A; Heber, V S; Jarzebinski, G; Mao, P H; Coath, C D; Kunihiro, T; Wiens, R C; Nordholt, J E; Moses, R W; Reisenfeld, D B; Jurewicz, A J G; Burnett, D S

    2011-06-24

    All planetary materials sampled thus far vary in their relative abundance of the major isotope of oxygen, (16)O, such that it has not been possible to define a primordial solar system composition. We measured the oxygen isotopic composition of solar wind captured and returned to Earth by NASA's Genesis mission. Our results demonstrate that the Sun is highly enriched in (16)O relative to the Earth, Moon, Mars, and bulk meteorites. Because the solar photosphere preserves the average isotopic composition of the solar system for elements heavier than lithium, we conclude that essentially all rocky materials in the inner solar system were enriched in (17)O and (18)O, relative to (16)O, by ~7%, probably via non-mass-dependent chemistry before accretion of the first planetesimals.

  15. The multiple sulfur isotopic composition of iron meteorites: Implications for nebular evolution

    NASA Astrophysics Data System (ADS)

    Antonelli, Michael Ariel

    2013-12-01

    Multiple sulfur isotopic measurements of troilite from 61 different iron meteorites were undertaken in order to test for sulfur isotopic homogeneity within (and between) 8 different iron meteorite groups. It was found that different members within a given group of iron meteorites have homogeneous Delta 33S compositions, but that these Delta33S compositions differ between groups. This thesis shows that iron meteorites from the groups IC, IIAB, IIIAB, IIIF, and IVA have small yet resolvable enrichments or depletions in Delta33S relative to Canyon Diablo Troilite (CDT) and troilite from other non-magmatic (IAB and IIE) iron meteorites. The observed anomalous sulfur isotopic compositions in magmatic iron meteorites are most consistent with Lyman-alpha photolysis of H2S, pointing towards inheritance of an unexpected photolytically-derived sulfur component in magmatic iron meteorite groups which is absent in non-magmatic iron meteorites, chondrites, and the Earth-Moon System.

  16. The carbon isotopic compositions of individual compounds from ancient and modern depositional environments

    SciTech Connect

    Freeman, K.H.

    1991-01-01

    This work examines factors influencing the isotopic compositions of individual compounds and, consequently, that of preserved sedimentary organic matter. Specifically, isotope effects associated with reactions resulting in the production and degradation of organic matter in the water column and reactions affecting preservation during diagenesis are considered in three projects. The first documents the preservation of the isotopic compositions of hydrocarbons altered by diagenetic reaction. Isotopic compositions of structurally-related polycyclic aromatic hydrocarbons (PAH) from the Messel Shale show little variation with increased unsaturation. The influence of environmental conditions on the isotopic composition of sedimentary organic carbon is documented by a comparison of the {delta}{sup 13}C of hydrocarbons in the marine Julia Creek Oil Shale and the lacustrine Condor Oil Shale. A model is proposed for identifying relative degrees of oxygenation and productivity within a paleoenvironment based on the observed {sup 13}C contents of biomarkers. Effects of processes proposed in the environmental model are documented by an examination of hydrocarbons from the waters and sediments of the Black Sea and of the Cariaco Trench. Sources of individual compounds are identified by comparison of their {sup 13}C content with that predicted for autotrophic biomass calculated from the concentration and {sup 13}C content of CO{sub 2}(aq) in the surface waters.

  17. SIMSISH Technique Does Not Alter the Apparent Isotopic Composition of Bacterial Cells

    PubMed Central

    Chapleur, Olivier; Wu, Ting-Di; Guerquin-Kern, Jean-Luc; Mazéas, Laurent; Bouchez, Théodore

    2013-01-01

    In order to identify the function of uncultured microorganisms in their environment, the SIMSISH method, combining in situ hybridization (ISH) and nanoscale secondary ion mass spectrometry (nanoSIMS) imaging, has been proposed to determine the quantitative uptake of specific labelled substrates by uncultured microbes at the single cell level. This technique requires the hybridization of rRNA targeted halogenated DNA probes on fixed and permeabilized microorganisms. Exogenous atoms are introduced into cells and endogenous atoms removed during the experimental procedures. Consequently differences between the original and the apparent isotopic composition of cells may occur. In the present study, the influence of the experimental procedures of SIMSISH on the isotopic composition of carbon in E. coli cells was evaluated with nanoSIMS and compared to elemental analyser-isotopic ratio mass spectrometer (EA-IRMS) measurements. Our results show that fixation and hybridization have a very limited, reproducible and homogeneous influence on the isotopic composition of cells. Thereby, the SIMSISH procedure minimizes the contamination of the sample by exogenous atoms, thus providing a means to detect the phylogenetic identity and to measure precisely the carbon isotopic composition at the single cell level. This technique was successfully applied to a complex sample with double bromine – iodine labelling targeting a large group of bacteria and a specific archaea to evaluate their specific 13C uptake during labelled methanol anaerobic degradation. PMID:24204855

  18. Accurate measurement of silver isotopic compositions in geological materials including low Pd/Ag meteorites

    NASA Astrophysics Data System (ADS)

    Woodland, S. J.; Rehkämper, M.; Halliday, A. N.; Lee, D.-C.; Hattendorf, B.; Günther, D.

    2005-04-01

    Very precise silver (Ag) isotopic compositions have been determined for a number of terrestrial rocks, and high and low Pd/Ag meteorites by utilizing multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). The meteorites include primitive chondrites, the Group IAB iron meteorites Canyon Diablo and Toluca, and the Group IIIAB iron meteorite Grant. Silver isotopic measurements are primarily of interest because 107Ag was produced by decay of the short-lived radionuclide 107Pd during the formation of the solar system and hence the Pd-Ag chronometer has set constraints on the timing of early planetesimal formation. A 2σ precision of ±0.05‰ can be obtained for analyses of standard solutions when Ag isotopic ratios are normalized to Pd, to correct for instrumental mass discrimination, and to bracketing standards. Caution must be exercised when making Ag isotopic measurements because isotopic artifacts can be generated in the laboratory and during mass spectrometry. The external reproducibility for geological samples based on replicate analyses of rocks is ±0.2‰ (2σ). All chondrites analyzed have similar Ag isotopic compositions that do not differ significantly (>0.3‰) from the 'terrestrial' value of the NIST SRM 978a Ag isotope standard. Hence, they show no evidence of excess 107Ag derived from 107Pd decay or, of stable Ag isotope fractionation associated with volatile element depletion within the accretion disk or from parent body metamorphism. The Group IAB iron meteorite samples analyzed show evidence of complex behavior and disturbance of Ag isotope systematics. Therefore, care must be taken when using this group of iron meteorites to obtain chronological information based on the Pd-Ag decay scheme.

  19. Long-term monitoring of stable isotopic compositions of precipitation over volcanic island, Jeju, Korea

    NASA Astrophysics Data System (ADS)

    Kim, Young-Hee; Koh, Dong-Chan; Park, Won-Bae; Bong, Yeon-Sik; Lee, Kwang-Sik; Lee, Jeonghoon

    2015-04-01

    Stable isotopic compositions of precipitation can be widely used to understand moisture transport in the atmosphere, proxies for paleoclimate and interactions between groundwater and precipitation. Over Jeju volcanic island, located southwest of the Korean Peninsula, precipitation penetrated directly into the highly permeable aquifer is the main source of groundwater. In this study, long-term stable isotopic compositions of precipitation over Jeju Island are characterized to describe spatial and temporal patterns for hydrology and paleoclimate. At fifteen sites from September 2000 to December 2003, precipitation samples were collected and analyzed by Isotope Ratio Mass Spectrometer at the Korea Basic Science Institute. Compared to Lee et al. (2003), the two seasonal local meteoric water lines widen, which may change the relative contributions of winter and summer season precipitation to the groundwater recharge. The precipitation isotopes are inversely correlated with precipitation amount in summer, whereas they do not show a strong correlation with surface air temperature. The precipitation isotopes monthly averaged relatively show a periodic function (R2=0.63 and 0.40 for hydrogen and oxygen, respectively), and deuterium excess (d-excess=δD-8×δ18O) shows a strong pattern of quadratic function (R2=0.97), which is related to a seasonal change of air masses. Altitude effect of precipitation isotopes, which can be a clue to reveal sources of groundwater, can be observed in every aspect of the volcanic island (for the oxygen isotope, -0.14‰ for east and west, -0.18‰ for north and -0.085‰ for south per 100 m). Our analysis of precipitation isotopes will be helpful to provide limitations and opportunities for paleoclimate reconstruction using isotopic proxies and water movement from atmosphere to subsurface.

  20. Uranium isotope compositions of the basaltic angrite meteorites and the chronological implications for the early Solar System.

    PubMed

    Brennecka, Gregory A; Wadhwa, Meenakshi

    2012-06-12

    Events occurring within the first 10 million years of the Solar System's approximately 4.5 billion-year history, such as formation of the first solids, accretion, and differentiation of protoplanetary bodies, have determined the evolutionary course of our Solar System and the planetary bodies within it. The application of high-resolution chronometers based on short-lived radionuclides is critical to our understanding of the temporal sequence of these critical events. However, to map the relative ages from such chronometers onto the absolute time scale, they must be "anchored" to absolute ages of appropriate meteoritic materials using the high-precision lead-lead (Pb-Pb) chronometer. Previously reported Pb-Pb dates of the basaltic angrite meteorites, some of which have been used extensively as time anchors, assumed a constant (238)U/(235)U ratio (= 137.88). In this work, we report measurements of (238)U/(235)U ratios in several angrites that are distinct from the previously assumed value, resulting in corrections to the Pb-Pb ages of ≥ 1 million years. There is no resolvable variation in the (238)U/(235)U ratio among the angrite bulk samples or mineral separates, suggesting homogeneity in the U isotopic composition of the angrite parent body. Based on these measurements, we recalculated the Pb-Pb age for the commonly used anchor, the D'Orbigny angrite, to be 4563.37 ± 0.25 Ma. An adjustment to the Pb-Pb age of a time anchor (such as D'Orbigny) requires a corresponding correction to the "model ages" of all materials dated using that anchor and a short-lived chronometer. This, in turn, has consequences for accurately defining the absolute timeline of early Solar System events.

  1. Uranium isotope compositions of the basaltic angrite meteorites and the chronological implications for the early Solar System

    PubMed Central

    Brennecka, Gregory A.; Wadhwa, Meenakshi

    2012-01-01

    Events occurring within the first 10 million years of the Solar System’s approximately 4.5 billion-year history, such as formation of the first solids, accretion, and differentiation of protoplanetary bodies, have determined the evolutionary course of our Solar System and the planetary bodies within it. The application of high-resolution chronometers based on short-lived radionuclides is critical to our understanding of the temporal sequence of these critical events. However, to map the relative ages from such chronometers onto the absolute time scale, they must be “anchored” to absolute ages of appropriate meteoritic materials using the high-precision lead–lead (Pb–Pb) chronometer. Previously reported Pb–Pb dates of the basaltic angrite meteorites, some of which have been used extensively as time anchors, assumed a constant 238U/235U ratio (= 137.88). In this work, we report measurements of 238U/235U ratios in several angrites that are distinct from the previously assumed value, resulting in corrections to the Pb–Pb ages of ≥1 million years. There is no resolvable variation in the 238U/235U ratio among the angrite bulk samples or mineral separates, suggesting homogeneity in the U isotopic composition of the angrite parent body. Based on these measurements, we recalculated the Pb–Pb age for the commonly used anchor, the D’Orbigny angrite, to be 4563.37 ± 0.25 Ma. An adjustment to the Pb–Pb age of a time anchor (such as D’Orbigny) requires a corresponding correction to the “model ages” of all materials dated using that anchor and a short-lived chronometer. This, in turn, has consequences for accurately defining the absolute timeline of early Solar System events. PMID:22647606

  2. Plutonium isotopes in the atmosphere of Central Europe: Isotopic composition and time evolution vs. circulation factors.

    PubMed

    Kierepko, Renata; Mietelski, Jerzy W; Ustrnul, Zbigniew; Anczkiewicz, Robert; Wershofen, Herbert; Holgye, Zoltan; Kapała, Jacek; Isajenko, Krzysztof

    2016-11-01

    This paper reports evidence of Pu isotopes in the lower part of the troposphere of Central Europe. The data were obtained based on atmospheric aerosol fraction samples collected from four places in three countries (participating in the informal European network known as the Ring of Five (Ro5)) forming a cell with a surface area of about 200,000km(2). We compared our original data sets from Krakow (Poland, 1990-2007) and Bialystok (Poland, 1991-2007) with the results from two other locations, Prague (Czech Republic; 1997-2004) and Braunschweig (Germany; 1990-2003) to find time evolution of the Pu isotopes. The levels of the activity concentration for (238)Pu and for ((239+240))Pu were estimated to be a few and some tens of nBqm(-3), respectively. However, we also noted some results were much higher (even about 70 times higher) than the average concentration of (238)Pu in the atmosphere. The achieved complex data sets were used to test a new approach to the problem of solving mixing isotopic traces from various sources (here up to three) in one sample. Results of our model, supported by mesoscale atmospheric circulation parameters, suggest that Pu from nuclear weapon accidents or tests and nuclear burnt-up fuel are present in the air.

  3. The effect of phosphomonoesterases on the oxygen isotope composition of phosphate

    NASA Astrophysics Data System (ADS)

    von Sperber, Christian; Kries, Hajo; Tamburini, Federica; Bernasconi, Stefano M.; Frossard, Emmanuel

    2014-01-01

    Plants and microorganisms under phosphorus (P) stress release extracellular phosphatases as a strategy to acquire inorganic phosphate (Pi). These enzymes catalyze the hydrolysis of phosphoesters leading to a release of Pi. During the enzymatic hydrolysis an isotopic fractionation (ε) occurs leaving an imprint on the oxygen isotope composition of the released Pi which might be used to trace phosphorus in the environment. Therefore, enzymatic assays with acid phosphatases from wheat germ and potato tuber and alkaline phosphatase from Escherichia coli were prepared in order to determine the oxygen isotope fractionation caused by these enzymes. Adenosine 5‧ monophosphate and glycerol phosphate were used as substrates. The oxygen isotope fractionation caused by acid phosphatases is 20-30‰ smaller than for alkaline phosphatases, resulting in a difference of 5-7.5‰ in δ18O of Pi depending on the enzyme. We attribute the enzyme dependence of the isotopic fractionation to distinct reaction mechanisms of the two types of phosphatases. The observed difference is large enough to distinguish between the two enzymatic processes in environmental samples. These findings show that the oxygen isotope composition of Pi can be used to trace different enzymatic processes, offering an analytical tool that might contribute to a better understanding of the P-cycle in the environment.

  4. Carbon isotope composition of latex does not reflect temporal variations of photosynthetic carbon isotope discrimination in rubber trees (Hevea brasiliensis).

    PubMed

    Kanpanon, Nicha; Kasemsap, Poonpipope; Thaler, Philippe; Kositsup, Boonthida; Gay, Frédéric; Lacote, Régis; Epron, Daniel

    2015-11-01

    Latex, the cytoplasm of laticiferous cells localized in the inner bark of rubber trees (Hevea brasiliensis Müll. Arg.), is collected by tapping the bark. Following tapping, latex flows out of the trunk and is regenerated, whereas in untapped trees, there is no natural exudation. It is still unknown whether the carbohydrates used for latex regeneration in tapped trees is coming from recent photosynthates or from stored carbohydrates, and in the former case, it is expected that latex carbon isotope composition of tapped trees will vary seasonally, whereas latex isotope composition of untapped trees will be more stable. Temporal variations of carbon isotope composition of trunk latex (δ(13)C-L), leaf soluble compounds (δ(13)C-S) and bulk leaf material (δ(13)C-B) collected from tapped and untapped 20-year-old trees were compared. A marked difference in δ(13)C-L was observed between tapped and untapped trees whatever the season. Trunk latex from tapped trees was more depleted (1.6‰ on average) with more variable δ(13)C values than those of untapped trees. δ(13)C-L was higher and more stable across seasons than δ(13)C-S and δ(13)C-B, with a maximum seasonal difference of 0.7‰ for tapped trees and 0.3‰ for untapped trees. δ(13)C-B was lower in tapped than in untapped trees, increasing from August (middle of the rainy season) to April (end of the dry season). Differences in δ(13)C-L and δ(13)C-B between tapped and untapped trees indicated that tapping affects the metabolism of both laticiferous cells and leaves. The lack of correlation between δ(13)C-L and δ(13)C-S suggests that recent photosynthates are mixed in the large pool of stored carbohydrates that are involved in latex regeneration after tapping.

  5. Moisture sources of precipitation over Postojna (Slovenia) and implication of its oxygen isotope composition

    NASA Astrophysics Data System (ADS)

    Krklec, Kristina; Domínguez-Villar, David; Lojen, Sonja

    2016-04-01

    The source of moisture is an important part of the hydrological cycle that affects climate system. Potentially, moisture sources are important controls of the isotope composition of precipitation, but their studies in the continental mid- and low-latitudes are still scarce due to the complexity of general circulation models with integrated isotope modules. We identify moisture uptake locations of precipitation over Postojna (Slovenia) for period from 2009 to 2013. By using HYSPLIT trajectory model of NOAA we did 5-day reconstruction of air mass history for the days with precipitation and determination of moisture uptake locations along back trajectories. Moisture uptake locations were identified along each trajectory using HYSPLIT output data and standard equations for saturation humidity mixing ratio, saturation vapour pressure and specific humidity. Although NNE winds were prevailing during the period 2001-2014, our analysis showed that during this period around 45% of the precipitation over Postojna originated from Mediterranean and south Atlantic area, with majority of locations originated in the Adriatic Sea. On the other hand, 41% of precipitation originated from moisture recycled over continents, predominantly from Pannonian basin. The comparison of monthly oxygen isotope composition of precipitation with the percentage of precipitation originated in different source regions shows a significant correlation only for the north Atlantic region. However, less than 7% of the variability of oxygen isotope composition of precipitation is associated with this moisture source. Multivariable analyses of source regions do not explain any additional variability of the oxygen isotope composition of precipitation over Postojna. This research shows that at this location, although significant, moisture sources are not important controls of the oxygen isotope composition of precipitation.

  6. Lead isotope studies of the Guerrero composite terrane, west-central Mexico: implications for ore genesis

    NASA Astrophysics Data System (ADS)

    Potra, Adriana; Macfarlane, Andrew W.

    2014-01-01

    New thermal ionization mass spectrometry and multi-collector inductively coupled plasma mass spectrometry Pb isotope analyses of three Cenozoic ores from the La Verde porphyry copper deposit located in the Zihuatanejo-Huetamo subterrane of the Guerrero composite terrane are presented and the metal sources are evaluated. Lead isotope ratios of 3 Cenozoic ores from the El Malacate and La Esmeralda porphyry copper deposits located in the Zihuatanejo-Huetamo subterrane and of 14 ores from the Zimapan and La Negra skarn deposits from the adjoining Sierra Madre terrane are also presented to look for systematic differences in the lead isotope trends and ore metal sources among the proposed exotic tectonostratigraphic terranes of southern Mexico. Comparison among the isotopic signatures of ores from the Sierra Madre terrane and distinct subterranes of the Guerrero terrane supports the idea that there is no direct correlation between the distinct suspect terranes of Mexico and the isotopic signatures of the associated Cenozoic ores. Rather, these Pb isotope patterns are interpreted to reflect increasing crustal contribution to mantle-derived magmas as the arc advanced eastward onto a progressively thicker continental crust. The lead isotope trend observed in Cenozoic ores is not recognized in the ores from Mesozoic volcanogenic massive sulfide and sedimentary exhalative deposits. The Mesozoic ores formed prior to the amalgamation of the Guerrero composite terrane to the continental margin, which took place during the Late Cretaceous, in intraoceanic island arc and intracontinental marginal basin settings, while the Tertiary deposits formed after this event in a continental arc setting. Lead isotope ratios of the Mesozoic and Cenozoic ores appear to reflect these differences in tectonic setting of ore formation. Most Pb isotope values of ores from the La Verde deposit (206Pb/204Pb = 18.674-18.719) are less radiogenic than those of the host igneous rocks, but plot within the

  7. Isotopic composition of Murchison organic compounds: Intramolecular carbon isotope fractionation of acetic acid. Simulation studies of cosmochemical organic syntheses

    NASA Technical Reports Server (NTRS)

    Yuen, G. U.; Cronin, J. R.; Blair, N. E.; Desmarais, D. J.; Chang, S.

    1991-01-01

    Recently, in our laboratories, samples of Murchison acetic acid were decarboxylated successfully and the carbon isotopic composition was measured for the methane released by this procedure. These analyses showed significant differences in C-13/C-12 ratios for the methyl and carboxyl carbons of the acetic acid molecule, strongly suggesting that more than one carbon source may be involved in the synthesis of the Murchison organic compounds. On the basis of this finding, laboratory model systems simulating cosmochemical synthesis are being studied, especially those processes capable of involving two or more starting carbon sources.

  8. Efficient mixing of the solar nebula from uniform Mo isotopic composition of meteorites.

    PubMed

    Becker, Harry; Walker, Richard J

    2003-09-11

    The abundances of elements and their isotopes in our Galaxy show wide variations, reflecting different nucleosynthetic processes in stars and the effects of Galactic evolution. These variations contrast with the uniformity of stable isotope abundances for many elements in the Solar System, which implies that processes efficiently homogenized dust and gas from different stellar sources within the young solar nebula. However, isotopic heterogeneity has been recognized on the subcentimetre scale in primitive meteorites, indicating that these preserve a compositional memory of their stellar sources. Small differences in the abundance of stable molybdenum isotopes in bulk rocks of some primitive and differentiated meteorites, relative to terrestrial Mo, suggest large-scale Mo isotopic heterogeneity between some inner Solar System bodies, which implies physical conditions that did not permit efficient mixing of gas and dust. Here we report Mo isotopic data for bulk samples of primitive and differentiated meteorites that show no resolvable deviations from terrestrial Mo. This suggests efficient mixing of gas and dust in the solar nebula at least to 3 au from the Sun, possibly induced by magnetohydrodynamic instabilities. These mixing processes must have occurred before isotopic fractionation of gas-phase elements and volatility-controlled chemical fractionations were established.

  9. Unexpected variations in the triple oxygen isotope composition of stratospheric carbon dioxide.

    PubMed

    Wiegel, Aaron A; Cole, Amanda S; Hoag, Katherine J; Atlas, Elliot L; Schauffler, Sue M; Boering, Kristie A

    2013-10-29

    We report observations of stratospheric CO2 that reveal surprisingly large anomalous enrichments in (17)O that vary systematically with latitude, altitude, and season. The triple isotope slopes reached 1.95 ± 0.05(1σ) in the middle stratosphere and 2.22 ± 0.07 in the Arctic vortex versus 1.71 ± 0.03 from previous observations and a remarkable factor of 4 larger than the mass-dependent value of 0.52. Kinetics modeling of laboratory measurements of photochemical ozone-CO2 isotope exchange demonstrates that non-mass-dependent isotope effects in ozone formation alone quantitatively account for the (17)O anomaly in CO2 in the laboratory, resolving long-standing discrepancies between models and laboratory measurements. Model sensitivities to hypothetical mass-dependent isotope effects in reactions involving O3, O((1)D), or CO2 and to an empirically derived temperature dependence of the anomalous kinetic isotope effects in ozone formation then provide a conceptual framework for understanding the differences in the isotopic composition and the triple isotope slopes between the laboratory and the stratosphere and between different regions of the stratosphere. This understanding in turn provides a firmer foundation for the diverse biogeochemical and paleoclimate applications of (17)O anomalies in tropospheric CO2, O2, mineral sulfates, and fossil bones and teeth, which all derive from stratospheric CO2.

  10. Isotope composition of sulphate in acid mine drainage as measure of bacterial oxidation

    USGS Publications Warehouse

    Taylor, B.E.; Wheeler, M.C.; Nordstrom, D.K.

    1984-01-01

    The formation of acid waters by oxidation of pyrite-bearing ore deposits, mine tailing piles, and coal measures is a complex biogeochemical process and is a serious environmental problem. We have studied the oxygen and sulphur isotope geochemistry of sulphides, sulphur, sulphate and water in the field and in experiments to identify sources of oxygen and reaction mechanisms of sulphate formation. Here we report that the oxygen isotope composition of sulphate in acid mine drainage shows a large variation due to differing proportions of atmospheric- and water-derived oxygen from both chemical and bacterially-mediated oxidation. 18O-enrichment of sulphate results from pyrite oxidation facilitated by Thiobacillus ferrooxidans in aerated environments. Oxygen isotope analysis may therefore be useful in monitoring the effectiveness of abatement programmes designed to inhibit bacterial oxidation. Sulphur isotopes show no significant fractionation between pyrite and sulphate, indicating the quantitative insignificance of intermediate oxidation states of sulphur under acid conditions. ?? 1984 Nature Publishing Group.

  11. Isotopic composition of precipitation in Northern Italy: Reverse effect of anomalous climatic events

    NASA Astrophysics Data System (ADS)

    Longinelli, A.; Anglesio, E.; Flora, O.; Iacumin, P.; Selmo, E.

    2006-10-01

    SummaryA few years ago the first comprehensive map of the isotopic composition of precipitation in Italy was published, based on the results obtained over several years at 77 different locations in Italy. The lack of financial support made it impossible to continue this study extended to the whole country. However, the collection of composite monthly samples continued at 12 locations in Northern Italy. The main purpose was to check the variability through time of the yearly mean isotopic values calculated for some of these stations according to previous data and to add a couple of stations in the western section of Alps, along the Italy-France border for which we had no data. We report here the data obtained for the years 2002-2004. This period is particularly interesting since, during 2003, most of Europe, and particularly Italy, experienced the hottest summer of the last century. In principle, this climatic event should have determined a marked enrichment in heavy isotopes in the annual weighted means for that year. On the contrary, all but one of the collection sites yielded yearly mean isotopic values that were considerably more negative than the mean values calculated for the previous years. This is essentially due to the marked decrease in the yearly amount of precipitation and particularly in that of spring and summer so that the mean weighted yearly isotopic values are heavily affected by the amount of precipitation and the isotopic values of the winter and autumn months. This shift was particularly marked at the collection sites located along the northern slope of the Apennines where a marked "shadow" effect related to westerly air masses moving over the Apennines exists. An important aspect of these data concerns the interpretation of isotopic values of palaeoprecipitation: in the case of palaeo-isotopic changes determined by environmental conditions similar to those reported here, a "normal" interpretation of the data may be misleading.

  12. The global iron budget: estimates of isotopic composition and elemental fluxes

    NASA Astrophysics Data System (ADS)

    Fantle, M. S.; Depaolo, D. J.

    2003-12-01

    Recent advances in the field of Fe isotope geochemistry show that isotope fractionation occurs under controlled conditions as a result of reduction, organic complexation, aqueous speciation, and/or hydroxide precipitation. These processes are integral to weathering, and are especially important for mobilizing Fe in an oxidizing environment. Our measurements of the Fe isotopic composition of soils, rivers, and marine sediments demonstrate significant isotopic variations (ca. 4‰ in 56Fe/54Fe) due to continental weathering. Based on these measurements, we hypothesize that dissolved Fe in rivers is variable but may be up to 3‰ lighter than igneous rocks. The flux and isotopic composition of dissolved riverine Fe could significantly affect the δ 56Fe of the ocean over geologic time, indicating changes in the productivity of the terrestrial biosphere or oxidation state at the Earth's surface. A preliminary global Fe budget is constructed for the modern oxidized surface Earth based on studies of global Fe fluxes in the literature. The total Fe flux to the modern ocean is dominated by riverine material, but the flux of dissolved Fe is roughly equally partitioned between atmospheric, riverine, and hydrothermal sources. There may be a significant diagenetic Fe flux to the water column from marine sediments, which we hypothesize has an Fe isotope composition that is substantially lighter than igneous rocks. A diagenetic Fe flux may be especially important in high productivity regions, such as the coastal ocean and enclosed near-shore basins, and during periods in Earth history when large portions of the ocean turn anoxic. The Fe isotopic signals of the diagenetic and riverine Fe fluxes, if preserved in the geologic record, may be useful for characterizing changing levels of biological productivity and oxidation state at the Earth's surface through time.

  13. Lithium contents and isotopic compositions of ferromanganese deposits from the global ocean

    USGS Publications Warehouse

    Chan, L.-H.; Hein, J.R.

    2007-01-01

    To test the feasibility of using lithium isotopes in marine ferromanganese deposits as an indicator of paleoceanographic conditions and seawater composition, we analyzed samples from a variety of tectonic environments in the global ocean. Hydrogenetic, hydrothermal, mixed hydrogenetic–hydrothermal, and hydrogenetic–diagenetic samples were subjected to a two-step leaching and dissolution procedure to extract first the loosely bound Li and then the more tightly bound Li in the Mn oxide and Fe oxyhydroxide. Total leachable Li contents vary from 2 by coulombic force. Hence, the abundant Li in hydrothermal deposits is mainly associated with the dominant phase, MnO2. The surface of amorphous FeOOH holds a slightly positive charge and attracts little Li, as demonstrated by data for hydrothermal Fe oxyhydroxide. Loosely sorbed Li in both hydrogenetic crusts and hydrothermal deposits exhibit Li isotopic compositions that resemble that of modern seawater. We infer that the hydrothermally derived Li scavenged onto the surface of MnO2 freely exchanged with ambient seawater, thereby losing its original isotopic signature. Li in the tightly bound sites is always isotopically lighter than that in the loosely bound fraction, suggesting that the isotopic fractionation occurred during formation of chemical bonds in the oxide and oxyhydroxide structures. Sr isotopes also show evidence of re-equilibration with seawater after deposition. Because of their mobility, Li and Sr in the ferromanganese crusts do not faithfully record secular variations in the isotopic compositions of seawater. However, Li content can be a useful proxy for the hydrothermal history of ocean basins. Based on the Li concentrations of the globally distributed hydrogenetic and hydrothermal samples, we estimate a scavenging flux of Li that is insignificant compared to the hydrothermal flux and river input to the ocean.

  14. In situ observations of the isotopic composition of methane at the Cabauw tall tower site

    NASA Astrophysics Data System (ADS)

    Röckmann, Thomas; Eyer, Simon; van der Veen, Carina; Popa, Maria E.; Tuzson, Béla; Monteil, Guillaume; Houweling, Sander; Harris, Eliza; Brunner, Dominik; Fischer, Hubertus; Zazzeri, Giulia; Lowry, David; Nisbet, Euan G.; Brand, Willi A.; Necki, Jaroslav M.; Emmenegger, Lukas; Mohn, Joachim

    2016-08-01

    High-precision analyses of the isotopic composition of methane in ambient air can potentially be used to discriminate between different source categories. Due to the complexity of isotope ratio measurements, such analyses have generally been performed in the laboratory on air samples collected in the field. This poses a limitation on the temporal resolution at which the isotopic composition can be monitored with reasonable logistical effort. Here we present the performance of a dual isotope ratio mass spectrometric system (IRMS) and a quantum cascade laser absorption spectroscopy (QCLAS)-based technique for in situ analysis of the isotopic composition of methane under field conditions. Both systems were deployed at the Cabauw Experimental Site for Atmospheric Research (CESAR) in the Netherlands and performed in situ, high-frequency (approx. hourly) measurements for a period of more than 5 months. The IRMS and QCLAS instruments were in excellent agreement with a slight systematic offset of (+0.25 ± 0.04) ‰ for δ13C and (-4.3 ± 0.4) ‰ for δD. This was corrected for, yielding a combined dataset with more than 2500 measurements of both δ13C and δD. The high-precision and high-temporal-resolution dataset not only reveals the overwhelming contribution of isotopically depleted agricultural CH4 emissions from ruminants at the Cabauw site but also allows the identification of specific events with elevated contributions from more enriched sources such as natural gas and landfills. The final dataset was compared to model calculations using the global model TM5 and the mesoscale model FLEXPART-COSMO. The results of both models agree better with the measurements when the TNO-MACC emission inventory is used in the models than when the EDGAR inventory is used. This suggests that high-resolution isotope measurements have the potential to further constrain the methane budget when they are performed at multiple sites that are representative for the entire European domain.

  15. Satellite measurements of the isotopic composition of galactic cosmic rays

    NASA Technical Reports Server (NTRS)

    Mewaldt, R. A.; Spalding, J. D.; Stone, E. C.; Vogt, R. E.

    1979-01-01

    The individual isotopes of galactic cosmic ray Ne, Mg, and Si at 100 MeV/nucleon were clearly resolved with an rms mass resolution of 0.20 amu. The results suggest the cosmic ray source is enriched in Ne-22, Mg-25, and Mg-26 when compared to the solar system. The ratio of (Mg-25)+(Mg-26) to Mg-24, which is approximately 0.49 compared to the solar system value of 0.27, suggest that the cosmic ray source and solar system material were synthesized under different conditions.

  16. Multiple sulfur isotope composition of oxidized Samoan melts and the implications of a sulfur isotope 'mantle array' in chemical geodynamics

    NASA Astrophysics Data System (ADS)

    Labidi, J.; Cartigny, P.; Jackson, M. G.

    2015-05-01

    To better address how subducted protoliths drive the Earth's mantle sulfur isotope heterogeneity, we report new data for sulfur (S) and copper (Cu) abundances, S speciation and multiple S isotopic compositions (32S, 33S, 34S, 36S) in 15 fresh submarine basaltic glasses from the Samoan archipelago, which defines the enriched-mantle-2 (EM2) endmember. Bulk S abundances vary between 835 and 2279 ppm. About 17 ± 11% of sulfur is oxidized (S6+) but displays no consistent trend with bulk S abundance or any other geochemical tracer. The S isotope composition of both dissolved sulfide and sulfate yield homogeneous Δ33S and Δ36S values, within error of Canyon Diablo Troilite (CDT). In contrast, δ34S values are variable, ranging between +0.11 and +2.79‰ (±0.12‰ 1σ) for reduced sulfur, whereas oxidized sulfur values vary between +4.19 and +9.71‰ (±0.80‰, 1σ). Importantly, δ34S of the reduced S pool correlates with the 87Sr/86Sr ratios of the glasses, in a manner similar to that previously reported for South-Atlantic MORB, extending the trend to δ34S values up to + 2.79 ± 0.04 ‰, the highest value reported for undegassed oceanic basalts. As for EM-1 basalts from the South Atlantic ridge, the linear δ34S-87Sr/86Sr trend requires the EM-2 endmember to be relatively S-rich, and only sediments can account for these isotopic characteristics. While many authors argue that both the EM-1 and EM-2 mantle components record subduction of various protoliths (e.g. upper or lower continental crust, lithospheric mantle versus intra-metasomatized mantle, or others), it is proposed here that they primarily reflect sediment recycling. Their distinct Pb isotope variation can be accounted for by varying the proportion of S-poor recycled oceanic crust in the source of mantle plumes.

  17. Isotopic composition analysis and age dating of uranium samples by high resolution gamma ray spectrometry

    NASA Astrophysics Data System (ADS)

    Apostol, A. I.; Pantelica, A.; Sima, O.; Fugaru, V.

    2016-09-01

    Non-destructive methods were applied to determine the isotopic composition and the time elapsed since last chemical purification of nine uranium samples. The applied methods are based on measuring gamma and X radiations of uranium samples by high resolution low energy gamma spectrometric system with planar high purity germanium detector and low background gamma spectrometric system with coaxial high purity germanium detector. The ;Multigroup γ-ray Analysis Method for Uranium; (MGAU) code was used for the precise determination of samples' isotopic composition. The age of the samples was determined from the isotopic ratio 214Bi/234U. This ratio was calculated from the analyzed spectra of each uranium sample, using relative detection efficiency. Special attention is paid to the coincidence summing corrections that have to be taken into account when performing this type of analysis. In addition, an alternative approach for the age determination using full energy peak efficiencies obtained by Monte Carlo simulations with the GESPECOR code is described.

  18. Constraints on Galactic Cosmic-Ray Origins from Elemental and Isotopic Composition Measurements

    NASA Technical Reports Server (NTRS)

    Binns, W. R.; Christian, E. R.; Cummings, A. C.; deNolfo, G. A.; Israel, M. H.; Leske, R. A.; Mewaldt, R. A,; Stone, E. C.; vonRosevinge, T. T.; Wiedenbeck, M. E.

    2013-01-01

    The most recent measurements by the Cosmic Ray Isotope Spectrometer (CRIS) aboard the Advanced Composition Explorer (ACE) satellite of ultra-heavy cosmic ray isotopic and elemental abundances will be presented. A range of isotope and element ratios, most importantly Ne-22/Ne-20, Fe-58/Fe-56, and Ga-31/Ge -32 show that the composition is consistent with source material that is a mix of approx 80% ISM (with Solar System abundances) and 20% outflow/ejecta from massive stars. In addition, our data show that the ordering of refractory and volatile elements with atomic mass is greatly improved when compared to an approx 80%/20% mix rather than pure ISM, that the refractory and volatile elements have similar slopes, and that refractory elements are preferentially accelerated by a factor of approx 4. We conclude that these data are consistent with an OB association origin of GCRs.

  19. The effect of different cooking processes on stable C, N, and H isotopic compositions of beef.

    PubMed

    Zhou, Jiuqing; Guo, Boli; Wei, Yimin; Zhang, Guoquan; Wei, Shuai; Ma, Yiyan

    2015-09-01

    The variability in the stable C, N, and H isotopic composition caused by different beef processing operations (boiling, frying, and roasting) was studied. The aim was to evaluate the stability of stable isotopic fingerprint information during the beef cooking process. The δ(13)C, δ(15)N, and δ(2)H values for raw, boiled, fried and roasted beef were measured, and the differences in the stable isotopic composition between raw and processed beef products were assessed. The results indicated that the δ(13)C and δ(15)N values in raw beef were not significantly different compared with processed beef, but the δ(2)H values were significantly higher in processed beef than in raw beef. In general, boiling, frying, and roasting had no significant effect on δ(13)C and δ(15)N values, but the δ(2)H value of processed beef increased.

  20. Isotopic composition of lead and strontium from Ascension and Gough Islands

    USGS Publications Warehouse

    Gast, P.W.; Tilton, G.R.; Hedge, C.

    1964-01-01

    Isotopic composition of lead and strontium has been determined in a series of rock samples from two islands on the Mid-Atlantic Ridge. Both inter-and intra-island variations exist in the abundance of radiogenic isotopes of both elements. Lead from basalt of Ascension Island has a Pb206-Pb 204 ratio of 19.5, while the corresponding ratio at Gough Island is only 18.4. The Pb208-Pb204 ratios from the two islands do not differ. Conversely, strontium from basalt of Ascension Island is less radiogenic than that from Gough Island basalts. The trachytes of both islands have lead and strontium that is more radiogenic than that found in the basalts. The inter-island differences indicate the existence of regional variations in the uranium-lead and rubidium-strontium ratios of the upper mantle source of these rocks and show that isotope compositions are a means for investigating chemical heterogeneities in the mantle.

  1. Carbon, hydrogen and nitrogen in carbonaceous chondrites Abundances and isotopic compositions in bulk samples

    NASA Technical Reports Server (NTRS)

    Kerridge, J. F.

    1985-01-01

    Whole-rock samples of 25 carbonaceous chondrites were analyzed for contents of C, H and N and delta C-13, delta D and delta N-15. Inhomogeneous distribution of these isotopes within individual meteorites is pronounced in several cases. Few systematic intermeteorite trends were observed; N data are suggestive of isotopic inhomogeneity in the early solar system. Several chondrites revealed unusual compositions which would repay further, more detailed study. The data are also useful for classification of carbonaceous chondrites; N abundance and isotopic compositions can differentiate existing taxonomic groups with close to 100 percent reliability; Al Rais and Renazzo clearly constitute a discrete 'grouplet', and there are hints that both CI and CM groups may each be divisible into two subgroups.

  2. Isotope variations of dissolved Zn in the Rio Grande watershed, USA: The role of adsorption on Zn isotope composition

    NASA Astrophysics Data System (ADS)

    Szynkiewicz, Anna; Borrok, David M.

    2016-01-01

    In order to better understand the factors influencing zinc (Zn) isotope composition in hydrological systems, we analyzed the δ66Zn of dissolved Zn in the streams and groundwater of the Upper and Middle Rio Grande watershed in Colorado and New Mexico, United States. The stream water samples have a wider variation of δ66Zn (-0.57 to + 0.41 ‰ relative to the JMC 3-0749-Lyon standard) than groundwater samples (-0.13 to + 0.12 ‰) and than samples from streams that are in close proximity to abandoned mining sites (+0.24 to + 0.40 ‰). Regional changes of bedrock geology, from primarily igneous rocks to primarily sedimentary rocks, have no resolvable effect on the δ66Zn of aqueous samples. Instead, an increase in water pH from 7.5 to 8.5 corresponds to a considerable decrease in the δ66Zn of dissolved Zn (R2 = - 0.37, p = 0.003, n = 22). Consequently, we link the observed Zn isotope variations to the process of adsorption of Zn onto suspended sediment and bedrock minerals (average Δ66Znadsorbed-dissolved = + 0.31 ‰). Our results are in good agreement with previous experimental and empirical studies suggesting that Zn adsorption leads to a residual dissolved pool enriched in light Zn isotopes. Given that anthropogenic Zn sources can also be responsible for lowering of δ66Zn, and may overlap with the pH/adsorption effect on δ66Zn, the latter needs to be carefully considered in future studies to differentiate between natural and anthropogenic factors influencing Zn isotopes in this and other aquatic systems.

  3. The isotopic composition of methane in polar ice cores

    NASA Technical Reports Server (NTRS)

    Craig, H.; Chou, C. C.; Welhan, J. A.; Stevens, C. M.; Engelkemeir, A.

    1988-01-01

    Air bubbles in polar ice cores indicate that about 300 years ago the atmospheric mixing ratio of methane began to increase rapidly. Today the mixing ratio is about 1.7 parts per million by volume, and, having doubled once in the past several hundred years, it will double again in the next 60 years if current rates continue. Carbon isotope ratios in methane up to 350 years in age have been measured with as little as 25 kilograms of polar ice recovered in 4-meter-long ice-core segments. The data show that: (1) in situ microbiology or chemistry has not altered the ice-core methane concentrations, and (2) that the carbon-13 to carbon-12 ratio of atmospheric CH4 in ice from 100 years and 300 years ago was about 2 per mil lower than at present. Atmospheric methane has a rich spectrum of isotopic sources: the ice-core data indicate that anthropogenic burning of the earth's biomass is the principal cause of the recent C-13H4 enrichment, although other factors may also contribute.

  4. The carbon isotope composition of atmospheric CO 2 in Paris

    NASA Astrophysics Data System (ADS)

    Widory, David; Javoy, Marc

    2003-10-01

    One characteristic of air pollution in the urban environment is high CO 2 concentrations resulting from human activities. Determining the relative contributions of the different CO 2 sources can be addressed simply and elegantly by combining isotope and concentration measurements. Using this approach on atmospheric CO 2 samples collected in Paris, its suburbs and the open country provides fairly accurate conclusions. Our results show that air pollution within the first few metres above ground results basically from binary mixtures among which road traffic is the main contributor and, in particular, vehicles using unleaded gasoline (˜90% of the total). Heating sources, which account for 50% of the CO 2 input below the atmospheric inversion level, and vehicles using diesel contribute very little. Human respiration has a recognisable signature at street level under certain circumstances. The combined isotope and concentration analysis provides a sensitive tracer of local variations, even detecting the occasional prevalence of human respiration and the onset of actions in which natural gas is burnt. It also detects surprising inlets of 'clean air' (CO 2-wise) in the very centre of the city.

  5. Sulphur isotopic compositions of deep-sea hydrothermal vent animals

    NASA Technical Reports Server (NTRS)

    Fry, B.; Gest, H.; Hayes, J. M.

    1983-01-01

    The S-34/S-32 ratios of tissues from vestimentiferan worms, brachyuran crabs, and giant clams living around deep hydrothermal vents are reported. Clean tissues were dried, ground, suspended in 0.1 M LiCl, shaken twice at 37 C to remove seawater sulfates, dried at 60 C, combusted in O2 in a Parr bomb. Sulfur was recovered as BaSO4, and the isotopic abundances in SO2 generated by thermal decomposition of 5-30-mg samples were determined using an isotope-ratio mass spectrometer. The results are expressed as delta S-34 and compared with values measured in seawater sulfates and in normal marine fauna. The values ranged from -4.7 to 4.7 per thousand, comparable to vent sulfide minerals (1.3-4.1 per thousand) and distinct from seawater sulfates (20.1 per thousand) and normal marine fauna (about 13-20 per thousand). These results indicate that vent sulfur rather than seawater sulfur is utilized by these animals, a process probably mediated by chemoautotrophic bacteria which can use inorganic sulfur compounds as energy sources.

  6. Stable water isotopic composition of the Antarctic subglacial Lake Vostok: implications for understanding the lake's hydrology.

    PubMed

    Ekaykin, Alexey A; Lipenkov, Vladimir Y; Kozachek, Anna V; Vladimirova, Diana O

    2016-01-01

    We estimated the stable isotopic composition of water from the subglacial Lake Vostok using two different sets of samples: (1) water frozen on the drill bit immediately after the first lake unsealing and (2) water frozen in the borehole after the unsealing and re-drilled one year later. The most reliable values of the water isotopic composition are: -59.0 ± 0.3 ‰ for oxygen-18, -455 ± 1 ‰ for deuterium and 17 ± 1 ‰ for d-excess. This result is also confirmed by the modelling of isotopic transformations in the water which froze in the borehole, and by a laboratory experiment simulating this process. A comparison of the newly obtained water isotopic composition with that of the lake ice (-56.2 ‰ for oxygen-18, -442.4 ‰ for deuterium and 7.2 ‰ for d-excess) leads to the conclusion that the lake ice is very likely formed in isotopic equilibrium with water. In turn, this means that ice is formed by a slow freezing without formation of frazil ice crystals and/or water pockets. This conclusion agrees well with the observed physical and chemical properties of the lake's accreted ice. However, our estimate of the water's isotopic composition is only valid for the upper water layer and may not be representative for the deeper layers of the lake, so further investigations are required.

  7. Neodymium isotopic composition of intermediate and deep waters in the glacial southwest Pacific

    NASA Astrophysics Data System (ADS)

    Noble, Taryn L.; Piotrowski, Alexander M.; McCave, I. Nick

    2013-12-01

    Neodymium (Nd) isotopes, tracers of deep water mass source and mixing, were measured on sedimentary planktic foraminifera with authigenic coatings from a depth-transect of cores (1400-4800 m) from Chatham Rise in the southwest Pacific, over the past 30 ka. We observe deglacial variations in the Nd isotopic composition, which showed an average glacial composition of ɛNd=-5.0 (1σ; ±0.3n=4) for cores sites below 3200 mbsl. No significant deglacial variation was observed in the Nd isotopic composition of intermediate depth waters (1400 mbsl), in contrast with benthic foraminifera δC13 data. The deglacial ɛNd shift of CDW in the southwest Pacific is consistent with changes observed in the deep South Atlantic and Equatorial Indian Ocean, but ɛNd values are offset by ˜1ɛNd-unit to more radiogenic values throughout the deglacial records, likely due to admixture of a Nd isotope signal which was modified in the Southern Ocean or Pacific, perhaps by boundary exchange. However, this modification did not overprint the deglacial Nd isotope change. The consistent deglacial evolution of ɛNd in the South Atlantic, Equatorial Indian and southwest Pacific CDW, is evidence for the connection of CDW during the glacial, and propagation of diminished North Atlantic Deep Water export to the glacial Southern Ocean. In contrast, spatial heterogeneities in the benthic foraminifera δC13 of CDW have been observed in the Atlantic, Indian and Pacific basins of the deep glacial Southern Ocean. The Nd isotope data implies a well-connected deep Southern Ocean, which transported waters from the Atlantic to the Indian and Pacific oceans, during the glacial. This suggests that basin-scale variability in the glacial δC13 composition of CDW was unrelated to circulation changes.

  8. Chemical and stable-radiogenic isotope compositions of Polatlı-Haymana thermal waters (Ankara, Turkey)

    NASA Astrophysics Data System (ADS)

    Akilli, Hafize; Mutlu, Halim

    2016-04-01

    Complex tectono-magmatic evolution of the Anatolian land resulted in development of numerous geothermal areas through Turkey. The Ankara region in central Anatolia is surrounded by several basins which are filled with upper Cretaceous-Tertiary sediments. Overlying Miocene volcanics and step faulting along the margins of these basins played a significant role in formation of a number of low-enthalpy thermal waters. In this study, chemical and isotopic compositions of Polatlı and Haymana geothermal waters in the Ankara region are investigated. The Polatlı-Haymana waters with a temperature range of 24 to 43 °C are represented by Ca-(Na)-HCO3 composition implying derivation from carbonate type reservoir rocks. Oxygen-hydrogen isotope values of the waters are conformable with the Global Meteoric Water Line and point to a meteoric origin. The carbon isotopic composition in dissolved inorganic carbon (DIC) of the studied waters is between -21.8 and -1.34 permil (vs. VPDB). Marine carbonates and organic rocks are the main sources of carbon. There is a high correlation between oxygen (3.7 to 15.0 permil; VSMOW) and sulfur (-9.2 to 19.5 permil; VCDT) isotope compositions of sulfate in waters. The mixing of sulfate from dissolution of marine carbonates and terrestrial evaporite units is the chief process behind the observed sulfate isotope systematics of the samples. 87Sr/86Sr ratios of waters varying from 0.705883 to 0.707827 are consistent with those of reservoir rocks. The temperatures calculated by SO4-H2O isotope geothermometry are between 81 and 138 °C nearly doubling the estimates from chemical geothermometers.

  9. Nitrogen sources and cycling in the San Francisco Bay estuary: A nitrate dual isotopic composition approach

    USGS Publications Warehouse

    Wankel, Scott D.; Kendall, C.; Francis, C.A.; Paytan, A.

    2006-01-01

    We used the dual isotopic composition of nitrate (??15N and ??18O) within the estuarine system of San Francisco (SF) Bay, California, to explore the utility of this approach for tracing sources and cycling of nitrate (NO3-). Surface water samples from 49 sites within the estuary were sampled during July-August 2004. Spatial variability in the isotopic composition suggests that there are multiple sources of nitrate to the bay ecosystem including seawater, several rivers and creeks, and sewage effluent. The spatial distribution of nitrate from these sources is heavily modulated by the hydrodynamics of the estuary. Mixing along the estuarine salinity gradient is the main control on the spatial variations in isotopic composition of nitrate within the northern arm of SF Bay. However, the nitrate isotopic composition in the southern arm of SF Bay exhibited a combination of source mixing and phytoplankton drawdown due mostly to the long residence time during the summer study period. Very low ?? 18ONO3 values (as low as -5.0???) at the Sacramento-San Joaquin River delta region give rise to a wide range of ??18ONO3 values in the SF Bay system. The range in ??18ONO3 values is more than twice that of (??15NNO3, suggesting that ??18O NO3 is an even more sensitive tool for tracing nitrate sources and cycling than ??15NNO3. ?? 2006, by the American Society of Limnology and Oceanography, Inc.

  10. Assembly and Study of Different Mercury Cells with Known Impurity Content and Isotopic Composition

    NASA Astrophysics Data System (ADS)

    Del Campo, D.; Chimenti, V.; Reyes, J.; Castrillón, J. A. Rodríguez; Moldovan, M.; Alonso, J. I. García

    2008-02-01

    The “Centro Español de Metrología” is carrying out a project to improve the knowledge of the influence of impurities and isotopic composition on the temperature of the mercury triple point. High-purity mercury from the Almaden mine (stated purity of 99.9998%) was further purified by vacuum distillation. Three mercury fractions, the original mercury from Almaden and two distilled fractions, were characterized in terms of both impurities and isotopic composition and used to measure the mercury triple point. The original mercury sample contained silver at 560 ng · g-1 as the main impurity while the impurity levels were much lower (silver < 1 ng · g-1) in the two distilled fractions. The isotopic composition of the distilled fractions showed delta values, expressed as 1,000×(^{198/202}Hg_sample-^{198/202} Hg_reference)/^{198/202}Hg_reference, of 1.37±0.07 (1 σ) for the first distilled sample and -1.55±0.03 (1 σ) for the second distilled sample with reference to the original Almaden mercury. For the measurement of the mercury triple point, an alcohol stirred bath was used that allowed two cells to be compared nearly simultaneously. It was observed that the presence of the silver impurities in the high-purity mercury modified slightly the mercury triple point while the effect of variations in the isotopic composition can be considered negligible.

  11. Soil moisture effects on the carbon isotopic composition of soil respiration

    EPA Science Inventory

    The carbon isotopic composition ( 13C) of recently assimilated plant carbon is known to depend on water-stress, caused either by low soil moisture or by low atmospheric humidity. Air humidity has also been shown to correlate with the 13C of soil respiration, which suggests indir...

  12. The atomic weight and isotopic composition of boron and their variation in nature

    SciTech Connect

    Holden, N.E.

    1993-08-01

    The boron isotopic composition and atomic weight value and their variation in nature are reviewed. Questions are raised about the previously recommended value and the uncertainty for the atomic weight. The problem of what constitutes an acceptable range for normal material and what should then be considered geologically exceptional is discussed. Recent measurements make some previous decisions in need of re-evaluation.

  13. Molecular Paleohydrology: Interpreting the Hydrogen-Isotopic Composition of Lipid Biomarkers from Photosynthesizing Organisms

    NASA Astrophysics Data System (ADS)

    Sachse, Dirk; Billault, Isabelle; Bowen, Gabriel J.; Chikaraishi, Yoshito; Dawson, Todd E.; Feakins, Sarah J.; Freeman, Katherine H.; Magill, Clayton R.; McInerney, Francesca A.; van der Meer, Marcel T. J.; Polissar, Pratigya; Robins, Richard J.; Sachs, Julian P.; Schmidt, Hanns-Ludwig; Sessions, Alex L.; White, James W. C.; West, Jason B.; Kahmen, Ansgar

    2012-05-01

    Hydrogen-isotopic abundances of lipid biomarkers are emerging as important proxies in the study of ancient environments and ecosystems. A decade ago, pioneering studies made use of new analytical methods and demonstrated that the hydrogen-isotopic composition of individual lipids from aquatic and terrestrial organisms can be related to the composition of their growth (i.e., environmental) water. Subsequently, compound-specific deuterium/hydrogen (D/H) ratios of sedimentary biomarkers have been increasingly used as paleohydrological proxies over a range of geological timescales. Isotopic fractionation observed between hydrogen in environmental water and hydrogen in lipids, however, is sensitive to biochemical, physiological, and environmental influences on the composition of hydrogen available for biosynthesis in cells. Here we review the factors and processes that are known to influence the hydrogen-isotopic compositions of lipids—especially n-alkanes—from photosynthesizing organisms, and we provide a framework for interpreting their D/H ratios from ancient sediments and identify future research opportunities.

  14. Habitat use and trophic position effects on contaminant bioaccumulation in fish indicated by stable isotope composition

    EPA Science Inventory

    The objective of our study was to determine the relationship between fish tissue stable isotope composition and total mercury or polychlorinated biphenyl (PCB) concentrations in a Great Lakes coastal food web. We sampled two resident fishes, Yellow Perch (Perca flavescens) and Bl...

  15. Summer precipitation influences the stable oxygen and carbon isotopic composition of tree-ring cellulose in Pinus ponderosa.

    PubMed

    Roden, John S; Ehleringer, James R

    2007-04-01

    The carbon and oxygen isotopic composition of tree-ring cellulose was examined in ponderosa pine (Pinus ponderosa Dougl.) trees in the western USA to study seasonal patterns of precipitation inputs. Two sites (California and Oregon) had minimal summer rainfall inputs, whereas a third site (Arizona) received as much as 70% of its annual precipitation during the summer months (North American monsoon). For the Arizona site, both the delta(18)O and delta(13)C values of latewood cellulose increased as the fraction of annual precipitation occurring in the summer (July through September) increased. There were no trends in latewood cellulose delta(18)O with the absolute amount of summer rain at any site. The delta(13)C composition of latewood cellulose declined with increasing total water year precipitation for all sites. Years with below-average total precipitation tended to have a higher proportion of their annual water inputs during the summer months. Relative humidity was negatively correlated with latewood cellulose delta(13)C at all sites. Trees at the Arizona site produced latewood cellulose that was significantly more enriched in (18)O compared with trees at the Oregon or California site, implying a greater reliance on an (18)O-enriched water source. Thus, tree-ring records of cellulose delta(18)O and delta(13)C may provide useful proxy information about seasonal precipitation inputs and the variability and intensity of the North American monsoon.

  16. Variations in the isotopic composition of stable mercury isotopes in typical mangrove plants of the Jiulong estuary, SE China.

    PubMed

    Sun, Lumin; Lu, Bingyan; Yuan, Dongxing; Hao, Wenbo; Zheng, Ying

    2017-01-01

    Variations in the composition of stable isotopes of mercury contained in tissues (root, stem, leaf, and hypocotyl or flower) of three typical mangrove plants (Kandelia candel, Aegiceras corniculata, and Bruguiera gymnorhiza), collected from the mangrove wetland of Jiulong estuary, SE China, were used to investigate the sources and transformation of mercury in the mangrove plants. Tissue samples from the plants were digested and mercury in the solution was pre-concentrated with purge-trap method and then analyzed by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The results showed that the mass dependent fractionation (MDF) of mercury ranged from -2.67 to -0.87 ‰ for δ (202)Hg while the mass independent fractionation (MIF) of mercury isotopes ranged from -0.16 to 0.09 and -0.19 to 0.05 ‰ for Δ(199)Hg and Δ(201)Hg, respectively, relative to the standard NIST SRM 3133. The ratio of Δ(199)Hg/Δ(201)Hg was 0.991, indicating that the mercury had been photo-reduced before being accumulated in mangrove plants. Analyses of the data from MIF studies revealed that the major portion of the mercury measured in leaves (∼90 %) originated from the atmosphere while the source of over half of the mercury present in roots was the surficial sediment. This study, the first of its kind investigating the variations in isotopic composition of mercury in the tissues of mangrove plants, could be helpful to identify the source of mercury contamination in mangroves and understand the biogeochemical cycle of mercury in the estuarine mangrove wetlands.

  17. High-precision measurements of seawater Pb isotope compositions by double spike thermal ionization mass spectrometry.

    PubMed

    Paul, Maxence; Bridgestock, Luke; Rehkämper, Mark; van DeFlierdt, Tina; Weiss, Dominik

    2015-03-10

    A new method for the determination of seawater Pb isotope compositions and concentrations was developed, which combines and optimizes previously published protocols for the separation and isotopic analysis of this element. For isotopic analysis, the procedure involves initial separation of Pb from 1 to 2L of seawater by co-precipitation with Mg hydroxide and further purification by a two stage anion exchange procedure. The Pb isotope measurements are subsequently carried out by thermal ionization mass spectrometry using a (207)Pb-(204)Pb double spike for correction of instrumental mass fractionation. These methods are associated with a total procedural Pb blank of 28±21 pg (1sd) and typical Pb recoveries of 40-60%. The Pb concentrations are determined by isotope dilution (ID) on 50 mL of seawater, using a simplified version of above methods. Analyses of multiple aliquots of six seawater samples yield a reproducibility of about ±1 to ±10% (1sd) for Pb concentrations of between 7 and 50 pmol/kg, where precision was primarily limited by the uncertainty of the blank correction (12±4 pg; 1sd). For the Pb isotope analyses, typical reproducibilities (±2sd) of 700-1500 ppm and 1000-2000 ppm were achieved for (207)Pb/(206)Pb, (208)Pb/(206)Pb and (206)Pb/(204)Pb, (207)Pb/(204)Pb, (208)Pb/(204)Pb, respectively. These results are superior to literature data that were obtained using plasma source mass spectrometry and they are at least a factor of five more precise for ratios involving the minor (204)Pb isotope. Both Pb concentration and isotope data, furthermore, show good agreement with published results for two seawater intercomparison samples of the GEOTRACES program. Finally, the new methods were applied to a seawater depth profile from the eastern South Atlantic. Both Pb contents and isotope compositions display a smooth evolution with depth, and no obvious outliers. Compared to previous Pb isotope data for seawater, the (206)Pb/(204)Pb ratios are well correlated

  18. The Influence of Kinetic Growth Factors on the Clumped Isotope Composition of Calcite

    NASA Astrophysics Data System (ADS)

    Hunt, J. D.; Watkins, J. M.; Tripati, A.; Ryerson, F. J.; DePaolo, D. J.

    2014-12-01

    Clumped isotope paleothermometry is based on the association of 13C and 18O within carbonate minerals. Although the influence of temperature on equilibrium 13C-18O bond ordering has been studied, recent oxygen isotope studies of inorganic calcite demonstrate that calcite grown in laboratory experiments and in many natural settings does not form in equilibrium with water. It is therefore likely that the carbon and clumped isotope composition of these calcite crystals are not representative of true thermodynamic equilibrium. To isolate kinetic clumped isotope effects that arise at the mineral-solution interface, clumped isotopic equilibrium of DIC species must be maintained. This can be accomplished by dissolving the enzyme carbonic anhydrase (CA) into the solution, thereby reducing the time required for isotopic equilibration of DIC species by approximately two orders of magnitude between pH 7.7 and 9.3. We conduct calcite growth experiments aimed specifically at measuring the pH-dependence of kinetic clumped isotope effects during non-equilibrium precipitation of calcite. We precipitated calcite from aqueous solution at a constant pH and controlled supersaturation over the pH range 7.7-9.3 in the presence of CA. For each experiment, a gas mixture of N2 and CO2 is bubbled through a beaker of solution without seed crystals. As CO2 from the gas dissolves into solution, calcite crystals grow on the beaker walls. The pH of the solution is maintained by use of an autotitrator with NaOH as the titrant. We control the temperature, pH, the pCO2 of the gas inflow, and the gas inflow rate, and monitor the total alkalinity, the pCO2 of the gas outflow, and the amount of NaOH added. A constant crystal growth rate of ~1.6 mmol/m2/hr is maintained over all experiments. Results from these experiments are compared to predictions from a recently-developed isotopic ion-by-ion growth model of calcite. The model describes the rate, temperature and pH dependence of oxygen isotope uptake

  19. Oxygenation of a Cryogenian ocean (Nanhua Basin, South China) revealed by pyrite Fe isotope compositions

    NASA Astrophysics Data System (ADS)

    Zhang, Feifei; Zhu, Xiangkun; Yan, Bin; Kendall, Brian; Peng, Xi; Li, Jin; Algeo, Thomas J.; Romaniello, Stephen

    2015-11-01

    The nature of ocean redox chemistry between the Cryogenian Sturtian and Marinoan glaciations (ca. 663-654 Ma) is important for understanding the relationship between environmental conditions and the subsequent emergence and expansion of early animals. The Cryogenian-to-Ediacaran stratigraphic succession of the Nanhua Basin in South China provides a nearly complete sedimentary record of the Cryogenian, including a continuous record of interglacial sedimentation. Here, we present a high-resolution pyrite Fe isotope record for a ∼120-m-long drill-core (ZK105) through Sturtian glacial diamictites and the overlying interglacial sediments in the Nanhua Basin to explore changes in marine chemistry during the late Cryogenian. Our pyrite Fe isotope profile exhibits significant stratigraphic variation: Interval I, comprising middle to upper Tiesi'ao diamictites (correlative with the Sturtian glaciation), is characterized by light, modern seawater-like Fe isotope compositions; Interval II, comprising uppermost Tiesi'ao diamictites and the basal organic-rich Datangpo Formation, is characterized by an abrupt shift to heavier Fe isotope compositions; and Interval III, comprising organic-poor grey shales in the middle Datangpo Formation, is characterized by the return of lighter, seawater-like Fe isotope compositions. We infer that Interval I pyrite was deposited in a predominantly anoxic glacial Nanhua Basin through reaction of dissolved Fe2+ and H2S mediated by microbial sulfate reduction (MSR). The shift to heavier pyrite Fe isotope values in Interval II is interpreted as partial oxidation of ferrous iron to ferric iron and subsequent near-quantitative reduction and transformation of Fe-oxyhydroxides to pyrite through coupling with oxidation of organic matter in the local diagenetic environment. In Interval III, near-quantitative oxidation of ferrous iron to Fe-oxyhydroxides followed by near-quantitative reduction and conversion to pyrite in the local diagenetic environment

  20. Hf isotope compositions of U.S. Geological Survey reference materials

    NASA Astrophysics Data System (ADS)

    Weis, Dominique; Kieffer, Bruno; Hanano, Diane; Nobre Silva, Inês; Barling, Jane; Pretorius, Wilma; Maerschalk, Claude; Mattielli, Nadine

    2007-06-01

    A systematic multi-isotopic and trace element characterization of U.S. Geological Survey reference materials has been carried out at the Pacific Centre for Isotopic and Geochemical Research, University of British Columbia. Values of 176Hf/177Hf are recommended for the following reference materials (mean ±2 SD): G-2: 0.282523 ± 6; G-3: 0.282518 ± 1; GSP-2: 0.281949 ± 8; RGM-1: 0.283017 ± 13; STM-1: 0.283019 ± 12; STM-2: 0.283021 ± 5; BCR-1: 0.282875 ± 8; BCR-2: 0.282870 ± 8; BHVO-1: 0.283106 ± 12; BHVO-2: 0.283105 ± 11; AGV-1: 0.282979 ± 6; and AGV-2: 0.282984 ± 9. Reproducibility is better than 50 ppm for the granitoid compositions and better than 40 ppm for the basaltic/andesitic compositions. For the isotopic analyses acquired early in this project on glass columns, Hf isotopic analyses from several of the reference materials were significantly less reproducible than Nd and Sr isotopic analyses determined from the same sample dissolution. The 176Hf/177Hf ratios for relatively radiogenic compositions (BCR-1, 2; BHVO-1, 2; RGM-1) were shifted systematically toward lower values by 100-150 ppm when a borosilicate primary column was used. Although systematic, the shift for felsic compositions was generally within analytical error, except for GSP-2, which has a very low Hf isotopic ratio, where the shift was to higher 176Hf/177Hf. Trace element and isotopic characterization of the borosilicate glass column, borosilicate frits, and quartz columns reveals extremely variable levels of trace elements. The 176Hf/177Hf ratios for these materials are very unradiogenic (borosilicate glass <0.28220 frit = 0.28193 ± 4). The borosilicate frit material appears to be the most variable in elemental concentration and isotopic composition. The quartz material has very low levels (

  1. Oxygen and nitrogen isotopic composition of nitrate in commercial fertilizers, nitric acid, and reagent salts.

    PubMed

    Michalski, Greg; Kolanowski, Michelle; Riha, Krystin M

    2015-01-01

    Nitrate is a key component of synthetic fertilizers that can be beneficial to crop production in agro-ecosystems, but can also cause damage to natural ecosystems if it is exported in large amounts. Stable isotopes, both oxygen and nitrogen, have been used to trace the sources and fate of nitrate in various ecosystems. However, the oxygen isotope composition of synthetic and organic nitrates is poorly constrained. Here, we present a study on the N and O isotope composition of nitrate-based fertilizers. The δ(15)N values of synthetic and natural nitrates were 0 ± 2 ‰ similar to the air N2 from which they are derived. The δ(18)O values of synthetic nitrates were 23 ± 3 ‰, similar to air O2, and natural nitrate fertilizer δ(18)O values (55 ± 5 ‰) were similar to those observed in atmospheric nitrate. The Δ(17)O values of synthetic fertilizer nitrate were approximately zero following a mass-dependent isotope relationship, while natural nitrate fertilizers had Δ(17)O values of 18 ± 2 ‰ similar to nitrate produced photochemically in the atmosphere. These narrow ranges of values can be used to assess the amount of nitrate arising from fertilizers in mixed systems where more than one nitrate source exists (soil, rivers, and lakes) using simple isotope mixing models.

  2. Nickel isotopic compositions of ferromanganese crusts and the constancy of deep ocean inputs and continental weathering effects over the Cenozoic

    NASA Astrophysics Data System (ADS)

    Gall, L.; Williams, H. M.; Siebert, C.; Halliday, A. N.; Herrington, R. J.; Hein, J. R.

    2013-08-01

    The global variability in nickel (Ni) isotope compositions in ferromanganese crusts is investigated by analysing surface samples of 24 crusts from various ocean basins by MC-ICPMS, using a double-spike for mass bias correction. Ferromanganese crusts have δ60Ni isotopic compositions that are significantly heavier than any other samples thus far reported (-0.1‰ to 0.3 ‰), with surface scrapings ranging between 0.9 ‰ and 2.5 ‰ (relative to NIST SRM986). There is no well resolved difference between ocean basins, although the data indicate somewhat lighter values in the Atlantic than in the Pacific, nor is there any evidence that the variations are related to biological fractionation, presence of different water masses, or bottom water redox conditions. Preliminary data for laterite samples demonstrate that weathering is accompanied by isotopic fractionation of Ni, which should lead to rivers and seawater being isotopically heavy. This is consistent with the slightly heavier than average isotopic compositions recorded in crusts that are sampled close to continental regions. Furthermore, the isotopic compositions of crusts growing close to a hydrothermal source are clustered around ∼ 1.5 ‰, suggesting that hydrothermal fluids entering the ocean may have a Ni isotopic composition similar to this value. Based on these data, the heavy Ni isotopic compositions of ferromanganese crusts are likely due to input of isotopically heavy Ni to the ocean from continental weathering and possibly also from hydrothermal fluids. A depth profile through one crust, CD29-2, from the north central Pacific Ocean displays large variations in Ni isotope composition (1.1 - 2.3 ‰) through the last 76 Myr. Although there may have been some redistribution of Ni associated with phosphatisation, there is no systematic difference in Ni isotopic composition between deeper, older parts and shallower, younger parts of the crust, which may suggest that oceanic sources and sinks of Ni have

  3. Noble gas isotopic composition as a key reference parameter in a planetary atmospheric evolution model

    NASA Astrophysics Data System (ADS)

    Ozima, M.

    2010-12-01

    The isotopic composition of noble gases is a key reference parameter in discussing the evolution of planetary atmospheres. Currently, two widely occurring noble gas components are identified in the early solar system, one is the Solar Wind noble gas (SW-noble gas, hereafter) and another is the Q-noble gas in unaltered meteorites: both noble gases are characterized by their ubiquitous occurrence and high isotopic homogeneity. Since the SW-noble gas is directly ejected from the Sun, it has been assumed to be a good proxy of the average noble gas isotopic composition in the Sun, namely the solar noble gas. The systematic enrichment of the heavier isotopes in the Q-noble gas relative to the SW-noble gas is then commonly attributed to its isotopic fractionation from the SW-noble gas. However, the isotopic compositions of the SW-noble gas either implanted on lunar soils or trapped by artificial targets show considerable isotopic variation depending on the velocity of the Solar Wind. Therefore, it is important to examine how closely the SW-noble gas represents the indigenous solar noble gas component or the mean isotopic composition of noble gases of the Sun. Here we show that the isotopic composition of the SW-noble gas is substantially fractionated relative to the solar value, and therefore should not be used as a reference parameter. We further suggest that the post D-burning Q-noble gas (see below) is the better proxy of the solar noble gas, and this should be used as a reference of the Solar noble gas isotopic composition in discussing the planetary atmospheric evolution. The most distinct difference between the Q- and the SW-noble gas is apparent in a 3He/4He isotopic ratio: 4.64e-4 in Q-He [1], but 1.23e-4 in SW-He[2]. The difference is attributed to the conversion of deuteron (D) to 3He in the Sun, namely the D-burning [3], due to high temperature during the pre-main sequence stage of the Sun. With the use of recent data on D/H ratios from helio-seismology [4] and

  4. Stable bromine isotopic composition of methyl bromide released from plant matter

    NASA Astrophysics Data System (ADS)

    Horst, Axel; Holmstrand, Henry; Andersson, Per; Thornton, Brett F.; Wishkerman, Asher; Keppler, Frank; Gustafsson, Örjan

    2014-01-01

    Methyl bromide (CH3Br) emitted from plants constitutes a natural source of bromine to the atmosphere, and is a component in the currently unbalanced global CH3Br budget. In the stratosphere, CH3Br contributes to ozone loss processes. Studies of stable isotope composition may reduce uncertainties in the atmospheric CH3Br budget, but require well-constrained isotope fingerprints of the source end members. Here we report the first measurements of stable bromine isotopes (δ81Br) in CH3Br from abiotic plant emissions. Incubations of both KBr-fortified pectin, a ubiquitous cell-stabilizing macromolecule, and of a natural halophyte (Salicornia fruticosa), yielded an enrichment factor (ε) of -2.00 ± 0.23‰ (1σ, n = 8) for pectin and -1.82 ± 0.02‰ (1σ, n = 4) for Salicornia (the relative amount of the heavier 81Br was decreased in CH3Br compared to the substrate salt). For short incubations, and up to 10% consumption of the salt substrate, this isotope effect was similar for temperatures from 30 up to 300 °C. For longer incubations of up to 90 h at 180 °C the δ81Br values increased from -2‰ to 0‰ for pectin and to -1‰ for Salicornia. These δ81Br source signatures of CH3Br formation from plant matter combine with similar data for carbon isotopes to facilitate multidimensional isotope diagnostics of the CH3Br budget.

  5. Coordinated Oxygen Isotopic and Petrologic Studies of CAIS Record Varying Composition of Protosolar

    NASA Technical Reports Server (NTRS)

    Simon, Justin I.; Matzel, J. E. P.; Simon, S. B.; Weber, P. K.; Grossman, L.; Ross, D. K.; Hutcheon, I. D.

    2012-01-01

    Ca-, Al-rich inclusions (CAIs) record the O-isotope composition of Solar nebular gas from which they grew [1]. High spatial resolution O-isotope measurements afforded by ion microprobe analysis across the rims and margin of CAIs reveal systematic variations in (Delta)O-17 and suggest formation from a diversity of nebular environments [2-4]. This heterogeneity has been explained by isotopic mixing between the O-16-rich Solar reservoir [6] and a second O-16-poor reservoir (probably nebular gas) with a "planetary-like" isotopic composition [e.g., 1, 6-7], but the mechanism and location(s) where these events occur within the protoplanetary disk remain uncertain. The orientation of large and systematic variations in (Delta)O-17 reported by [3] for a compact Type A CAI from the Efremovka reduced CV3 chondrite differs dramatically from reports by [4] of a similar CAI, A37 from the Allende oxidized CV3 chondrite. Both studies conclude that CAIs were exposed to distinct, nebular O-isotope reservoirs, implying the transfer of CAIs among different settings within the protoplanetary disk [4]. To test this hypothesis further and the extent of intra-CAI O-isotopic variation, a pristine compact Type A CAI, Ef-1 from Efremovka, and a Type B2 CAI, TS4 from Allende were studied. Our new results are equally intriguing because, collectively, O-isotopic zoning patterns in the CAIs indicate a progressive and cyclic record. The results imply that CAIs were commonly exposed to multiple environments of distinct gas during their formation. Numerical models help constrain conditions and duration of these events.

  6. The Suess Effect and Additional Impacts on the Carbon Isotope Composition of a Belizean Coral

    NASA Astrophysics Data System (ADS)

    Greer, L.; Bunn, S.; Humston, R.; Swart, P. K.; Curran, H.; Rose, L. E.

    2011-12-01

    Recent work has shown that the geochemistry of coral skeletons can reflect large-scale changes in the ocean carbon isotope budget as influenced by the anthropogenic influx of fossil fuel carbon to the atmosphere (the Suess Effect). Yet not all coral carbon records reflect just atmospheric controls on carbon. This study assesses the relative influence of the Suess Effect on carbon chemistry within a Belizean Montastrea faveolota colony and interprets deviations from the Suess Effect signal. The coral sample used for this study was collected off Wee Wee Caye, in South-Central Belize offshore of the Sittee River, Stann Creek District in 2003. Coral carbonate was sampled at an average resolution of 15 samples per coral year. Carbon isotope data from the Belizean coral were compared with mean annual carbon isotope data from Atlantic corals in a study by Swart et. al (2010) to analyze the relative contribution of the Suess Effect and competing controls on the carbon isotope composition of Belizean waters. The observed pattern in the Belize coral suggested two distinct trends in carbon isotopic composition, and segmented regression analysis indicated a significant breakpoint occurs in this record in approximately 1965. Deforestation rates in Belize after the 1960's have been almost double that for the rest of Central America (2.3% vs. 1.2% annually) corresponding with a general shift from rural farming to large scale agriculture in Belize. Consequently, increased rates of deforestation in Belize may have been an important factor in carbon isotope budgets of the area over the last several decades. Compared with data averaged from Atlantic coral samples, annual carbon isotope values in Belizean coral declined more rapidly since the 1960's. We attribute this sharper decline in the Belizean coral to enhanced influx of terrestrial 'light' organic carbon to the reef over the study period.

  7. Carbon and hydrogen isotopic compositions of algae and bacteria from hydrothermal environments, Yellowstone National Park

    NASA Astrophysics Data System (ADS)

    Estep, Marilyn L. F.

    1984-03-01

    Stromatolites forming today on a small scale in hydrothermal environments are chemical and biological analogues of much larger Precambrian formations. Carbon isotopic composition varied as a function of CO 2 concentration, pH, and species composition. Stratiform, layered stromatolites grew in silica-depositing springs at 55° to 70°C; they consisted mainly of a unicellular alga, Synechococcus, and a filamentous, photosynthetic bacterium, Chloroflexus. These thermophiles become enriched in 12C as the concentration of carbon dioxide in the effluent waters increases. At a concentration of 40 ppm total inorganic C, and δ 13C of organic carbon was ˜ -12%., whereas at 900 ppm total inorganic C, the δ 13C of similar species was ˜ -25%.. Conical stromatolites or conophytons (principally a filamentous, blue-green alga Phormidium and Chloroflexus) grew at 40°-55°C. In older, broader conophytons, Chloroflexus was the dominant organism. Their δ 13C values were ˜ -18%. in a variety of hot springs. In carbonate-depositing springs, i.e., carbon dioxide saturated, conophytons and stromatolites consisting of a variety of blue-green algae and photosynthetic bacteria had the most negative δ 13C values (to -30%.). These carbon isotope ratios are directly comparable to carbon isotope ratios of kerogen from Precambrian stromatolites. The presence and activity of methanogenic bacteria or heterotrophic, aerobic and anaerobic bacteria did not alter significantly the δ 13C of the original organic matter. The hydrogen isotopic fractionation between thermophilic organisms and water is 0 to -74 for temperatures of 85° to 46°C, respectively. Acidophilic algae fractionated hydrogen isotopes to a lesser extent than did the photosynthetic organisms inhabiting neutral pH springs. Because organic matter retains some of its original isotopic signature, relationships of CO 2 levels, pH, temperature, and species composition between modern stromatolites and their environment and those of

  8. Regulation of Isotopic Composition of Water - way of Improvement of Cosmonauts Drinking Water Functional Properties

    NASA Astrophysics Data System (ADS)

    Kulikova, Ekaterina; Utina, Dina; Vorozhtsova, Svetlana; Severyuhin, Yuri; Abrosimova, Anna; Sinyak, Yuri; Ivanov, Alexander

    The problem in providing drinking water to cosmonauts is solved - at this moment there is a task to improve the functional properties of the water. One of the perspectives of this trend is the use of light isotopic water. The animal studies have shown that long-term consumption of water with a depletion of deuterium and oxygen heavy isotopes accelerates the rise of mass non-irradiated mice, the phase fluctuations reducing or increasing hematological parameters were having adaptive nature. These fluctuations didn’t overcome values beyond the physiological norm of this type of animal. It is established that the therapeutic use of light isotopic water with 35 - 90 ppm in deuterium increases the survival of irradiated mice by an average of 30%, contributes to the preservation of irradiated animals body weight. Treatment of acute radiation sickness with light isotopic water stimulates hematopoietic recovery. At the same time, keeping mice drinking light isotopic water for 7 - 8 days before the irradiation (from 4 to 8.5 Gr) has no effect on the level of radio resistance. Longer keeping mice on light isotopic water, for 14 -21 days - reduction in life expectancy, animal mass, bone marrow cellularity and the level of white blood cells in irradiated animals is noted. It was established that keeping mice on light isotopic water for 14 days before exposure in experimental animals causes an increase in the mitotic index and the frequency of formation of aberrant mitosis after 24 hours of Co(60) gamma radiation in doses of 1 , 2, and 4 Gr. Thus, it is clear that the regulation of the isotopic composition of drinking water - way to improve its functional properties.

  9. Isotopic Composition of Gaseous Elemental Mercury (Hg0) at Various Sites in Japan

    NASA Astrophysics Data System (ADS)

    Yamakawa, A.; Moriya, K.; Yoshinaga, J.

    2015-12-01

    Mercury (Hg) is a toxic heavy metal, which exists in various chemical forms in the environmental system. In the atmosphere, Hg exists in three forms (Hg0(g), Hg+2(g), and Hg(p)). Hg0(g) is the dominant species of atmospheric Hg, accounting for >95% of the total Hg in the atmosphere. Because Hg0(g) is highly volatile and has limited solubility in water, it cannot be easily removed by wet or dry deposition processes. Therefore, the residence time of Hg0(g) in the atmosphere is relatively long (1 to 2 years), allowing long-range transport from mercury emission source(s). Conversely, Hg+2(g) and Hg(p) are effectively removed from the atmosphere through wet and dry depositions. The determination of mercury source attribution using quantitative data is challenging because Hg0(g) may be deposited on an area upon oxidation to Hg+2(g) and associated with aerosols and particulates to form Hg(p) while the global cycling of Hg0(g). Over the last decade, the development of analytical methods of highly precise Hg isotopic measurements demonstrated mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) of Hg isotopes in environmental samples. For instance, MDF of Hg isotopes is thought to occur during various natural and industrial Hg transformations. MIF of Hg isotopes is observed during abiotic reduction, photochemical and non-photochemical, and physical and chemical processes. Such processes lead to differences in the Hg isotopic composition of different emission sources, both natural and anthropogenic, and atmospheric processes (i.e., transportation, oxidation/reduction, deposition, and reemission). Therefore, Hg isotopic compositions could be used to trace the sources and processes of atmospheric Hg. For securing the reliability and accuracy of atmospheric Hg isotope data, the methods of collection, pretreatment, and isotopic measurement for Hg0(g) were developed to obtain high recovery yield of samples with no Hg isotopic fractionation during each

  10. Isotopic composition of Mg and Fe in garnet peridotites from the Kaapvaal and Siberian cratons

    NASA Astrophysics Data System (ADS)

    An, Yajun; Huang, Jin-Xiang; Griffin, W. L.; Liu, Chuanzhou; Huang, Fang

    2017-03-01

    We present Mg and Fe isotopic data for whole rocks and separated minerals (olivine, clinopyroxene, orthopyroxene, garnet, and phlogopite) of garnet peridotites that equilibrated at depths of 134-186 km beneath the Kaapvaal and Siberian cratons. There is no clear difference in δ26Mg and δ56Fe of garnet peridotites from these two cratons. δ26Mg of whole rocks varies from -0.243‰ to -0.204‰ with an average of -0.225 ± 0.037‰ (2σ, n = 19), and δ56Fe from -0.038‰ to 0.060‰ with an average of -0.003 ± 0.068‰ (2σ, n = 19). Both values are indistinguishable from the fertile upper mantle, indicating that there is no significant Mg-Fe isotopic difference between the shallow and deep upper mantle. The garnet peridotites from ancient cratons show δ26Mg similar to komatiites and basalts, further suggesting that there is no obvious Mg isotopic fractionation during different degrees of partial melting of deep mantle peridotites and komatiite formation. The precision of the Mg and Fe isotope data (⩽±0.05‰ for δ26Mg and δ56Fe, 2σ) allows us to distinguish inter-mineral isotopic fractionations. Olivines are in equilibrium with opx in terms of Mg and Fe isotopes. Garnets have the lowest δ26Mg and δ56Fe among the coexisting mantle minerals, suggesting the dominant control of crystal structure on the Mg-Fe isotopic compositions of garnets. Elemental compositions and mineralogy suggest that clinopyroxene and garnet were produced by later metasomatic processes as they are not in chemical equilibrium with olivine or orthopyroxene. This is consistent with the isotopic disequilibrium of Mg and Fe isotopes between orthopyroxene/olivine and garnet/clinopyroxene. Combined with one sample showing slightly heavy δ26Mg and much lighter δ56Fe, these disequilibrium features in the garnet peridotites reveal kinetic isotopic fractionation due to Fe-Mg inter-diffusion during reaction between peridotites and percolating melts in the Kaapvaal craton.

  11. Mineralogy and Oxygen Isotope Compositions of Two C-Rich Hydrated Interplanetary Dust Particles

    NASA Technical Reports Server (NTRS)

    Snead, C. J.; McKeegan, K. D.; Messenger, S.; Nakamura-Messenger, K.

    2012-01-01

    Oxygen isotopic compositions of chondrites reflect mixing between a O-16-rich reservoir and a O-17,O-18-rich reservoir produced via mass-independent fractionation. The composition of the O-16-rich reservoir is reasonably well constrained, but material representing the O-17,O-18-rich end-member is rare. Self-shielding models predict that cometary water, presumed to represent this reservoir, should be enriched in O-17 and O-18 18O by > 200%. Hydrated interplanetary dust particles (IDPs) rich in carbonaceous matter may be derived from comets; such particles likely contain the products of reaction between O-16-poor water and anhydrous silicates that formed in the inner solar system. Here we present mineralogy and oxygen isotope compositions of two C-rich hydrated IDPs, L2083E47 and L2071E35.

  12. A non-terrestrial 16O-rich isotopic composition for the protosolar nebula.

    PubMed

    Hashizume, Ko; Chaussidon, Marc

    2005-03-31

    The discovery in primitive components of meteorites of large oxygen isotopic variations that could not be attributed to mass-dependent fractionation effects has raised a fundamental question: what is the composition of the protosolar gas from which the host grains formed? This composition is probably preserved in the outer layers of the Sun, but the resolution of astronomical spectroscopic measurements is still too poor to be useful for comparison with planetary material. Here we report a precise determination of the oxygen isotopic composition of the solar wind from particles implanted in the outer hundreds of nanometres of metallic grains in the lunar regolith. These layers of the grains are enriched in 16O by >20 +/- 4 per thousand relative to the Earth, Mars and bulk meteorites, which implies the existence in the solar accretion disk of reactions--as yet unknown--that were able to change the 17O/16O and 18O/16O ratios in a way that was not dependent strictly on the mass of the isotope. Photochemical self-shielding of the CO gas irradiated by ultraviolet light may be one of these key processes, because it depends on the abundance of the isotopes, rather than their masses.

  13. X-ray diffraction characterization of epitaxial CVD diamond films with natural and isotopically modified compositions

    NASA Astrophysics Data System (ADS)

    Prokhorov, I. A.; Voloshin, A. E.; Ralchenko, V. G.; Bolshakov, A. P.; Romanov, D. A.; Khomich, A. A.; Sozontov, E. A.

    2016-11-01

    Comparative investigations of homoepitaxial diamond films with natural and modified isotopic compositions, grown by chemical vapor deposition (CVD) on type-Ib diamond substrates, are carried out using double-crystal X-ray diffractometry and topography. The lattice mismatch between the substrate and film is precisely measured. A decrease in the lattice constant on the order of (Δ a/ a)relax ˜ (1.1-1.2) × 10-4 is recorded in isotopically modified 13C (99.96%) films. The critical thicknesses of pseudomorphic diamond films is calculated. A significant increase in the dislocation density due to the elastic stress relaxation is revealed by X-ray topography.

  14. The Oxygen Isotopic Composition of MIL 090001: A CR2 Chondrite with Abundant Refractory Inclusions

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.; McKeegan, K. D.; Sharp, Z. D.

    2012-01-01

    MIL 090001 is a large (>6 kg) carbonaceous chondrite that was classified as a member of the CV reduced subgroup (CVred) that was recovered during the 2009-2010 ANSMET field season [1]. Based on the abundance of refractory inclusions and the extent of aqueous alteration, Keller [2] suggested a CV2 classification. Here we report additional mineralogical and petrographic data for MIL 090001, its whole-rock oxygen isotopic composition and ion microprobe analyses of individual phases. The whole rock oxygen isotopic analyses show that MIL 090001 should be classified as a CR chondrite.

  15. Preservation of Earth-forming events in the tungsten isotopic composition of modern flood basalts.

    PubMed

    Rizo, Hanika; Walker, Richard J; Carlson, Richard W; Horan, Mary F; Mukhopadhyay, Sujoy; Manthos, Vicky; Francis, Don; Jackson, Matthew G

    2016-05-13

    How much of Earth's compositional variation dates to processes that occurred during planet formation remains an unanswered question. High-precision tungsten isotopic data from rocks from two large igneous provinces, the North Atlantic Igneous Province and the Ontong Java Plateau, reveal preservation to the Phanerozoic of tungsten isotopic heterogeneities in the mantle. These heterogeneities, caused by the decay of hafnium-182 in mantle domains with high hafnium/tungsten ratios, were created during the first ~50 million years of solar system history, indicating that portions of the mantle that formed during Earth's primary accretionary period have survived to the present.

  16. Preservation of Earth-forming events in the tungsten isotopic composition of modern flood basalts

    NASA Astrophysics Data System (ADS)

    Rizo, Hanika; Walker, Richard J.; Carlson, Richard W.; Horan, Mary F.; Mukhopadhyay, Sujoy; Manthos, Vicky; Francis, Don; Jackson, Matthew G.

    2016-05-01

    How much of Earth's compositional variation dates to processes that occurred during planet formation remains an unanswered question. High-precision tungsten isotopic data from rocks from two large igneous provinces, the North Atlantic Igneous Province and the Ontong Java Plateau, reveal preservation to the Phanerozoic of tungsten isotopic heterogeneities in the mantle. These heterogeneities, caused by the decay of hafnium-182 in mantle domains with high hafnium/tungsten ratios, were created during the first ~50 million years of solar system history, indicating that portions of the mantle that formed during Earth’s primary accretionary period have survived to the present.

  17. Southern Greenland water vapour isotopic composition at the crossroads of Atlantic and Arctic moisture

    NASA Astrophysics Data System (ADS)

    Bonne, J. L.; Steen-Larsen, H. C.; Risi, C. M.; Werner, M.; Sodemann, H.; Lacour, J. L.; Fettweis, X.; Cesana, G.; Delmotte, M.; Cattani, O.; Clerbaux, C.; Sveinbjörnsdottir, A. E.; Masson-Delmotte, V.

    2014-12-01

    Since September 2011, a continuous water vapour isotopic composition monitoring instrument has been remotely operated in Ivittuut (61.21°N, 48.17°W), southern Greenland. Meteorological parameters are monitored and precipitation has been sampled and analysed for isotopic composition, suggesting equilibrium between surface vapour and precipitation. The data depict small summer diurnal variations. δ18O and deuterium excess (d-excess) are generally anti-correlated and show important seasonal variations (with respective amplitudes of 10 and 20 ‰), and large synoptic variations associated to low-pressure systems (typically +5‰ on δ18O and -15‰ on d-excess). The moisture sources, estimated based on Lagrangian back-trajectories, are primarily influenced by the western North Atlantic, and north-eastern American continent. Notable are important seasonal and synoptic shifts of the moisture sources, and sporadic influences of the Arctic or the eastern North Atlantic. Moisture sources variations can be related to changes in water vapour isotopic composition, and the isotopic fingerprints can be attributed to the areas of moisture origins. Isotopic enabled AGCMs nudged to meteorology (LMDZiso, ECHAM5-wiso), despite biases, correctly capture the δ18O changes, but underestimate the d-excess changes. They allow to identify a high correlation between the southern Greenland d-excess and the simulated relative humidity and d-excess in the moisture source region south of Greenland. An extreme high temperature event in July 2012 affecting all Greenland, similar to ice sheet melt events during the medieval periods and one event in 1889 documented by Greenland ice core records, has been analysed regarding water vapour isotopic composition, using remote sensing (IASI) and in situ observations from Bermuda to northern Greenland (NEEM station). Our southern Greenland observations allow to track the water vapour evolution during this event along the moisture transport path

  18. Rare gas systematics in popping rock: isotopic and elemental compositions in the upper mantle

    PubMed

    Moreira; Kunz; Allegre

    1998-02-20

    New experimental data on the isotopic variations of neon, argon, and xenon in a popping rock imply that the 40Ar/36Ar ratio of the upper mantle is less than 44,000 and that the 129Xe/130Xe ratio is less than 8.2. The elemental abundance pattern of rare gases is chondritic-like and is quite distinct from the solar pattern. These data imply that Earth accreted from planetesimals that probably underwent a transformation of their rare gas budget from solar- to chondritic-like, leaving the isotopic composition unchanged from the solar pattern.

  19. Concentration and isotopic composition of carbon and sulfur in apollo 11 lunar samples.

    PubMed

    Kaplan, I R; Smith, J W

    1970-01-30

    The concentration of carbon and sulfur in six samples ranged between 20 to 200 and 650 to 2300 parts per million, respectively. Carbon was present in gaseous, volatilizable, and nonvolatile forms, and terrestrial contaminants were recognized. Sulfur appeared to exist only as acid-volatile sulfide. The bulk fines contain a high concentration of carbon and a low concentration of sulfur. They are always enriched in the heavier isotope carbon-13 or sulfur-34. The fine-grained basaltic rocks show the reverse relation; lowest carbon, highest sulfide concentrations, and no apparent enrichment in heavy isotopes. The breccias are of intermediate composition.

  20. Absolute Quantification of Prion Protein (90-231) Using Stable Isotope-Labeled Chymotryptic Peptide Standards in a LC-MRM AQUA Workflow

    NASA Astrophysics Data System (ADS)

    Sturm, Robert; Sheynkman, Gloria; Booth, Clarissa; Smith, Lloyd M.; Pedersen, Joel A.; Li, Lingjun

    2012-09-01

    Substantial evidence indicates that the disease-associated conformer of the prion protein (PrPTSE) constitutes the etiologic agent in prion diseases. These diseases affect multiple mammalian species. PrPTSE has the ability to convert the conformation of the normal prion protein (PrPC) into a β-sheet rich form resistant to proteinase K digestion. Common immunological techniques lack the sensitivity to detect PrPTSE at subfemtomole levels, whereas animal bioassays, cell culture, and in vitro conversion assays offer higher sensitivity but lack the high-throughput the immunological assays offer. Mass spectrometry is an attractive alternative to the above assays as it offers high-throughput, direct measurement of a protein's signature peptide, often with subfemtomole sensitivities. Although a liquid chromatography-multiple reaction monitoring (LC-MRM) method has been reported for PrPTSE, the chemical composition and lack of amino acid sequence conservation of the signature peptide may compromise its accuracy and make it difficult to apply to multiple species. Here, we demonstrate that an alternative protease (chymotrypsin) can produce signature peptides suitable for a LC-MRM absolute quantification (AQUA) experiment. The new method offers several advantages, including: (1) a chymotryptic signature peptide lacking chemically active residues (Cys, Met) that can confound assay accuracy; (2) low attomole limits of detection and quantitation (LOD and LOQ); and (3) a signature peptide retaining the same amino acid sequence across most mammals naturally susceptible to prion infection as well as important laboratory models. To the authors' knowledge, this is the first report on the use of a non-tryptic peptide in a LC-MRM AQUA workflow.

  1. Hydrogeochemical and Isotopic Composition of Pasinler Geothermal Water (Erzurum, Turkey)

    NASA Astrophysics Data System (ADS)

    Hatipoglu, E.; Sunnetci, M. O.; Gultekin, F.

    2013-12-01

    In this investigation Pasinler (Erzurum) hot water spring has been studied from the point of geology and environmental isotopes. The Pasinler geothermal field is located 37 km east of Erzurum Province. The basement of Pasinler Geothermal field consists of Upper Cretaceous ophiolitic melange, shale, claystone, marl, and limestones, Eocene gabbro, andesite, basalt, trachyandesite, Oligocene andesite and basalt, Lower Miocene reef limestones, Upper Miocene pyroclastics, Plio- Quaternary (sandstone, marl, conglomerate) and Quaternary alluvium. The rhyolite is the reservoir for the geothermal fluid. The tuffs and marls are cap rocks of the system. The fault and related fractures around the Pasinler geothermal field provide pathways for the upward flow of geothermal fluid to the surface. The Alluvium around the Hasankale River is the most important unit as cold groundwater deposits in the study area. The thermal waters in the Pasinler geothermal fields have outlet temperatures of 23 to 35°C in springs. But discharge temperatures in the wells vary between 38-52°C. Geothermal well waters belong to the Na-Ca-Cl-HCO3 type. The Pasinler geothermal water has discharge pH values of 6 to 6.6, electrical conductivity (EC) of 970 to 6233 μS/cm, and TDS values between 635 and 4304 mg/l. δ18O, δ2H and δ3H isotope analyses were carried out to determine the origin of waters, recharge altitude, precipitation types, and groundwater circulation. In the 18O-δ 2H diagram all of the waters in the study area situated near the Globol Meteoric Water Line (GMWL) and indicate meteoric origin with little to no evaporation. According to the δ18O - temperature relation all water samples recharged at the same elevation in the plain. Low tritium coupled with high electrical conductivity and high Cl-value in the Pasinler thermal spring indicate that this spring has deep circulation. In order to determinate the origin of sulphure (SO4) and carbon in the waters, all waters were analysed for

  2. Temperature and Oxygen Isotope Composition of The Ediacaran Ocean: Constraints From Clumped Isotope Carbonate Thermometry

    NASA Astrophysics Data System (ADS)

    Bonifacie, M.; Eiler, J. M.; Fike, D. A.

    2008-12-01

    The temperature and chemical variations of the early oceans on Earth are highly debated, particularly for periods associated with significant evolutionary change and/or extinction. The temperature of past oceans has been estimated based on conventional carbonate-water and/or silicate-water stable oxygen isotope thermometry. Precambrian carbonates and silicates both exhibit a long-term secular trend of increasing δ18O values with decreasing age. This trend has been used to support two opposite - though related - interpretations: the Earth's oceans gradually cooled over the course of the Proterozoic eon, from a maximum of ~ 60-90°C at ~ 2.5Ga (and were, on average, relatively warm during much of the Paleozoic era) [1]. This interpretation has been supported by Si-isotope proxies and the thermal tolerances of proteins in various classes of microbial organisms [2-3]. Alternatively, the δ18O value of the oceans has gradually increased through time [4-5], and mean Earth surface temperatures varied over a narrow range similar to modern conditions. In other terms, one either assumes an ocean of constant δ18O and infers that climate varied dramatically, or vise versa. Finally, it is possible that post- depositional processes (e.g., diagenesis, burial metamorphism, weathering) has modified the δ18O values of all or most Precambrian sedimentary carbonates and silicates, overprinting any paleoclimatic variations. Carbonate 'clumped isotope' thermometry provides a new way to independently test these hypotheses because it allows one to determine the apparent growth temperatures of carbonate minerals based on their abundances of 13C-18O bonds, as reflected by the 'Δ47' value of CO2 extracted by phosphoric acid digestion [6]. This method is thermodynamically based and independent of the δ18O of water from which the carbonate grew. We will report the initial results of measurements of 'Δ47 for a suite of carbonates from the Sultanate of Oman. This Ediacaran age (~ 635 to

  3. Stable isotope composition of waters in the Great Basin, United States 1. Air-mass trajectories

    USGS Publications Warehouse

    Friedman, I.; Harris, J.M.; Smith, G.I.; Johnson, C.A.

    2002-01-01

    Isentropic trajectories, calculated using the NOAA/Climate Monitoring and Diagnostics Laboratory's isentropic transport model, were used to determine air-parcel origins and the influence of air mass trajectories on the isotopic composition of precipitation events that occurred between October 1991 and September 1993 at Cedar City, Utah, and Winnemucca, Nevada. Examination of trajectories that trace the position of air parcels backward in time for 10 days indicated five distinct regions of water vapor origin: (1) Gulf of Alaska and North Pacific, (2) central Pacific, (3) tropical Pacific, (4) Gulf of Mexico, and (5) continental land mass. Deuterium (??D) and oxygen-18 (??18O) analyses were made of precipitation representing 99% of all Cedar City events. Similar analyses were made on precipitation representing 66% of the precipitation falling at Winnemucca during the same period. The average isotopic composition of precipitation derived from each water vapor source was determined. More than half of the precipitation that fell at both sites during the study period originated in the tropical Pacific and traveled northeast to the Great Basin; only a small proportion traversed the Sierra Nevada. The isotopic composition of precipitation is determined by air-mass origin and its track to the collection station, mechanism of droplet formation, reequilibration within clouds, and evaporation during its passage from cloud to ground. The Rayleigh distillation model can explain the changes in isotopic composition of precipitation as an air mass is cooled pseudo-adiabatically during uplift. However, the complicated processes that take place in the rapidly convecting environment of cumulonimbus and other clouds that are common in the Great Basin, especially in summer, require modification of this model because raindrops that form in the lower portion of those clouds undergo isotopic change as they are elevated to upper levels of the clouds from where they eventually drop to the

  4. A Record of Oceanic Lithium Isotope Composition for the Last 7Ma

    NASA Astrophysics Data System (ADS)

    Marriott, C. S.; Henderson, G. M.

    2003-12-01

    Continental weathering plays an important role in global climate change but has proved difficult to reconstruct for the past. New geological tools with which to assess the past rate and style of weathering are therefore urgently required. One such tool is Li isotope fractionation. Recent studies [1,2] have shown preferential release of 7Li into the aqueous phase and retention/adsorption of 6Li during weathering processes such as partial dissolution and secondary mineral formation. Lithium behaves conservatively in the oceans, with a residence time of ˜1Ma, so that a history of ocean Li isotope composition provides information about the average rate and style of global continental weathering on long timescales. The incorporation of lithium as a trace element in marine carbonates enables the construction of a record of oceanic Li-isotopic variation and is the focus of this work. Carbonate Li-isotope compositions are lighter than seawater by ˜8 per mil, but this fractionation is not temperature dependent. This has been demonstrated by measurement of Li isotopes in inorganically precipitated calcites (5-30° C) [3], in coralline aragonite (25-30° C) [3] and in benthic foraminifera Uvigerina (7-23° C). This lack of T-dependent fractionation suggests that the variation in the isotope composition of planktonic foraminifera will solely reflect changes in oceanic Li isotope composition, which in turn is strongly influence by changes in continental weathering. ODP site 758, located on the Ninetyeast Ridge in the Indian Ocean (5° N, 90° E; 2925m), was sampled at 2m intervals, over a depth corresponding to the last 7Ma, to produce 55 samples with a temporal resolution of approximately 130Ka. Site 758 is previously well studied with an existing chronology and high resolution Sr, O and Nd isotope data. Individual foram species in the core top were first investigated to assess inter-species fractionation effects. Down core lithium isotope variation was examined by

  5. Constraints from loess on the Hf-Nd isotopic composition of the upper continental crust

    NASA Astrophysics Data System (ADS)

    Chauvel, Catherine; Garçon, Marion; Bureau, Sarah; Besnault, Adeline; Jahn, Bor-ming; Ding, Zhongli

    2014-02-01

    Knowledge of the average composition of the upper continental crust is crucial to establish not only how it formed but also when. While well constrained averages have been suggested for its major and trace element composition, no values exist for its Nd and Hf isotopic compositions even though radiogenic isotopic systems provide valuable information on its average model age. Here we present Nd and Hf isotopic data determined on a large number of loess deposits from several continents. We demonstrate that these deposits have very uniform Nd and Hf isotopic compositions. We obtain an average Nd isotopic composition that is similar to previous estimates for the upper continental crust (εNd=-10.3±1.2(1σ)) and we establish a new Hf average value at εHf=-13.2±2(1σ). This average falls on the “Terrestrial Array”, demonstrating that the two parent-daughter ratios are not decoupled during crust formation. Trace element data acquired on the same set of samples allow us to calculate an average 147Sm/144Nd ratio for the upper continental crust: 0.1193±0.0026, a value slightly higher than previous estimates. Based on the relationship between Sm/Nd and Nd isotopes, we estimate the average Nd extraction age of upper continental crust from the depleted mantle at TDM(Nd)=1.82±0.07 Ga. This model age is entirely consistent with previous suggestions made for example by Goldstein et al. (1984). Assuming that for each individual sample, the Hf model age cannot be younger than the Nd model age, our new Nd-Hf isotopic data provide a value for the very poorly known 176Lu/177Hf ratio of the upper crust. Our estimate is 176Lu/177Hf = 0.0125 ± 0.0018, a value significantly lower than commonly used values (0.0150-0.0159; Griffin et al., 2002; Goodge and Vervoort, 2006; Hawkesworth et al., 2010) but higher than Rudnick and Gao's (2003) estimate of 0.0083. The impact of our new 176Lu/177Hf ratio on crustal model ages of zircon populations is not simple to evaluate but the Hf model

  6. Predicting the Isotopic Composition of Subduction-Filtered Subducted Oceanic Crust and Sediment

    NASA Astrophysics Data System (ADS)

    White, W. M.

    2010-12-01

    The chemical and isotopic character of mantle plumes, which produce oceanic island volcanoes, are widely thought to reflect the presence of recycled oceanic crust and sediment. Isotopic systematics suggest the “cycle time” for this process is 1 Ga or longer, but it should be possible to use a simple mass balance approach to discern how the presently operating subduction zone filter affects the ratios of radioactive parent to radiogenic daughter isotopes. Simple uniformitarian assumptions can then be used to predict the present isotopic composition of anciently subducted lithosphere. Our underlying assumption in deciphering the subduction zone filter is that the flux of an element into the deep mantle is simply equal to the flux of element into the subduction zone less the flux of that element into subduction zone magmas. The former is readily calculated from published data. The latter can be calculated by estimating parental magma compositions, arc accretion rates, and the assumption that arc magma compositions differ from MORB only because of material derived from subducting crust and sediment. Using this approach for 8 intra-oceanic subduction zones, we find 73% of Th and Pb, 79% of U, 80% of Rb and Sr, 93% of Nd and 98% of Sm survive the subduction zone filter. The subduction zone filter systematically increases Sm/Nd ratios in all subduction zones, but the effect is small, with a weighted mean increase of 1.5%. The effect of subduction is to decrease the Sm/Nd of the mantle, but only slightly. The effect of subduction is to increase the Rb/Sr of the mantle, but the subduction zone filter does not have a systematic effect on Rb/Sr ratios: it significantly increases in Rb/Sr in 3 subduction zones and significantly decreases it in one; the weighted mean shows no significant change. The effect of the subduction zone filter on U/Pb is also not systematic. U/Pb ratios in the mantle fluxes are bimodal, with values equal to or lower than the bulk Earth value in 4

  7. Thallium isotope composition of the upper continental crust and rivers - An investigation of the continental sources of dissolved marine thallium

    USGS Publications Warehouse

    Nielsen, S.G.; Rehkamper, M.; Porcelli, D.; Andersson, P.; Halliday, A.N.; Swarzenski, P.W.; Latkoczy, C.; Gunther, D.

    2005-01-01

    The thallium (Tl) concentrations and isotope compositions of various river and estuarine waters, suspended riverine particulates and loess have been determined. These data are used to evaluate whether weathering reactions are associated with significant Tl isotope fractionation and to estimate the average Tl isotope composition of the upper continental crust as well as the mean Tl concentration and isotope composition of river water. Such parameters provide key constraints on the dissolved Tl fluxes to the oceans from rivers and mineral aerosols. The Tl isotope data for loess and suspended riverine detritus are relatively uniform with a mean of ??205Tl = -2.0 ?? 0.3 (??205Tl represents the deviation of the 205Tl/203Tl isotope ratio of a sample from NIST SRM 997 Tl in parts per 104). For waters from four major and eight smaller rivers, the majority were found to have Tl concentrations between 1 and 7 ng/kg. Most have Tl isotope compositions very similar (within ??1.5 ??205Tl) to that deduced for the upper continental crust, which indicates that no significant Tl isotope fractionation occurs during weathering. Based on these results, it is estimated that rivers have a mean natural Tl concentration and isotope composition of 6 ?? 4 ng/kg and ??205Tl = -2.5 ?? 1.0, respectively. In the Amazon estuary, both additions and losses of Tl were observed, and these correlate with variations in Fe and Mn contents. The changes in Tl concentrations have much lower amplitudes, however, and are not associated with significant Tl isotope effects. In the Kalix estuary, the Tl concentrations and isotope compositions can be explained by two-component mixing between river water and a high-salinity end member that is enriched in Tl relative to seawater. These results indicate that Tl can display variable behavior in estuarine systems but large additions and losses of Tl were not observed in the present study. Copyright ?? 2005 Elsevier Ltd.

  8. Evidence of a systematic deviation of the isotopic composition of neon from commercial sources compared with its isotopic composition in air.

    PubMed

    Pavese, Franco; Fellmuth, Bernd; Head, David I; Hermier, Yves; Hill, Kenneth D; Valkiers, Staf

    2005-08-01

    Results are reported of a study concerning the variation in isotopic composition of a limited number of neon samples of commercial origin and the resulting influence on the temperature of the triple point of this element. All seven neon samples investigated were found to contain more 22Ne than neon in air, and the amount fraction of 22Ne varied by as much as 0.2% from sample to sample. This variation corresponds to a range of triple-point temperatures (Ttp) of more than 200 microK, much larger than the state-of-the-art uncertainty in the realization of this phase transition for metrological purposes. Deviations in the amount fractions of 21Ne were irrelevant, as far as their effect on T(tp) is concerned, though they may have relevance to other isotope studies. Ratios of amounts of neon isotopes at IRMM-Geel were obtained using the same measurement procedures, and instrumentation developed in the framework of the redetermination of the Avogadro constant and all significant sources of uncertainty were taken into account. The repeatability of the ion current ratio measurements on individual samples was 5 x 10(-5) relative. All uncertainty statements are made following the ISO/BIPM Guide to the Expression of Uncertainty in Measurements. Whereas these results proved unexpected, a more comprehensive study will follow incorporating a much wider range of samples of commercial origin.

  9. Isotopic compositions of bismuth, lead, thallium, and mercury from mini r-processing

    NASA Technical Reports Server (NTRS)

    Heymann, D.; Liffman, K.

    1986-01-01

    The yields of stable isotopes of Bi, Pb, Tl and Hg as well as yields of Pb-205 are calculated with a parametrized model for 'mini r-processing' in the Ne, O, C-rich zones of explosive burning in massive stars. The Pb isotopic compositions stand out by their comparatively low Pb-207 yields and by the fact that this r-process variant yields Pb-204 quite abundantly. The average Pb-205/Pb-204 yield ratio of 6.1 is the same order of magnitude as yield ratios deduced for s-processing. The Hg from this mini r-process looks like normal solar-system mercury, but with Hg-196 missing and the light s-isotopes A = 198, 199, 200 and 201 depleted (especially the odd-A species).

  10. Sr and Nd isotope composition of deformed peridotite xenoliths from Udachnaya kimberlite pipe

    NASA Astrophysics Data System (ADS)

    Surgutanova, E. A.; Agashev, A. M.; Demonterova, E. I.; Golovin, A. V.; Pokhilenko, N. P.

    2016-11-01

    New results of Rb-Sr and Sm-Nd isotope analyses have been obtained on samples of deformed peridotite xenoliths collected from the Udachnaya kimberlite pipe (Yakutia). The data obtained imply two main stages of metasomatic alteration of the lithospheric mantle base matter in the central part of the Siberian Craton. Elevated ratios of Sr isotopes may be considered as evidence of an ancient stage of metasomatic enrichment by a carbonatite melt. The acquired Nd isotope composition together with the geochemistry of the deformed peridotite xenoliths suggests that the second stage of metasomatic alteration took place shortly before formation of the kimberlite melt. The metasomatic agent of this stage had a silicate character and arrived from an asthenosphere source, common for the normal OIB type (PREMA) and the Group-I kimberlite.

  11. PC/FRAM: New capabilities for the gamma-ray spectrometry measurement of plutonium isotopic composition

    SciTech Connect

    Sampson, T.E.; Kelley, T.A.; Cremers, T.L.; Konkel, T.R.; Friar, R.J.

    1995-10-01

    We describe the new capability of and.present measurement results from the PC/FRAM plutonium isotopic analysis code. This new code allows data acquisition from a single coaxial germanium detector and analysis over an energy range from 120 keV to above I MeV. For the first time we demonstrate a complete isotopic analysis using only gamma rays greater than 200 keV in energy. This new capability allows the measurement of the plutonium isotopic composition of items inside shielded or heavy-walled containers without having to remove the items from the container. This greatly enhances worker safety by reducing handling and the resultant radiation exposure. Another application allows international inspectors to verify the contents of items inside sealed, long-term storage containers that may not be opened for national security or treaty compliance reasons. We present measurement results for traditional planar germanium detectors as well as coaxial detectors measuring shielded and unshielded samples.

  12. Isotopic compositions of bismuth, lead, thallium, and mercury from mini r-processing

    NASA Astrophysics Data System (ADS)

    Heymann, D.; Liffman, K.

    1986-03-01

    The yields of stable isotopes of Bi, Pb, Tl and Hg as well as yields of Pb-205 are calculated with a parametrized model for 'mini r-processing' in the Ne, O, C-rich zones of explosive burning in massive stars. The Pb isotopic compositions stand out by their comparatively low Pb-207 yields and by the fact that this r-process variant yields Pb-204 quite abundantly. The average Pb-205/Pb-204 yield ratio of 6.1 is the same order of magnitude as yield ratios deduced for s-processing. The Hg from this mini r-process looks like normal solar-system mercury, but with Hg-196 missing and the light s-isotopes A = 198, 199, 200 and 201 depleted (especially the odd-A species).

  13. The chlorine isotope composition of the moon and implications for an anhydrous mantle.

    PubMed

    Sharp, Z D; Shearer, C K; McKeegan, K D; Barnes, J D; Wang, Y Q

    2010-08-27

    Arguably, the most striking geochemical distinction between Earth and the Moon has been the virtual lack of water (hydrogen) in the latter. This conclusion was recently challenged on the basis of geochemical data from lunar materials that suggest that the Moon's water content might be far higher than previously believed. We measured the chlorine isotope composition of Apollo basalts and glasses and found that the range of isotopic values [from -1 to +24 per mil (per thousand) versus standard mean ocean chloride] is 25 times the range for Earth. The huge isotopic spread is explained by volatilization of metal halides during basalt eruption--a process that could only occur if the Moon had hydrogen concentrations lower than those of Earth by a factor of approximately 10(4) to 10(5), implying that the lunar interior is essentially anhydrous.

  14. Isotopic composition of Antarctic Dry Valley nitrate: Implications for NOy sources and cycling in Antarctica

    USGS Publications Warehouse

    Michalski, G.; Bockheim, James G.; Kendall, C.; Thiemens, M.

    2005-01-01

    Nitrates minerals from the Dry Valleys of Antarctica have been analyzed for their oxygen and nitrogen isotopic compositions. The 15N was depleted with δ15N values ranging from −9.5 to −26.2‰, whereas the 17O and 18O isotopes were highly enriched (with excess 17O) with δ18O values spanning 62–76‰ and Δ17O values from 28.9 to 32.7‰. These are the largest 17O enrichments observed in any known mineral. The oxygen isotopes indicate that nitrate is from a combination of tropospheric transport of photochemically produced HNO3 and HNO3 formed in the stratosphere.

  15. Carbon isotope composition of low molecular weight hydrocarbons and monocarboxylic acids from Murchison meteorite

    NASA Technical Reports Server (NTRS)

    Yuen, G.; Blair, N.; Des Marais, D. J.; Chang, S.

    1984-01-01

    Carbon isotopic compositions have been measured for individual hydrocarbons and monocarboxylic acids from the Murchison meteorite, a C2 carbonaceous chondrite which fell in Australia in 1969. With few exceptions, notably benzene, the volatile products are substantially isotopically heavier than their terrestrial counterparts, signifying their extraterrestrial origin. For both classes of compounds, the ratio of C-13 to C-12 decreases with increasing carbon number in a roughly parallel manner, and each carboxylic acid exhibits a higher isotopic ratio than the hydrocarbon containing the same number of carbon atoms. These trends are consistent with the kinetically controlled synthesis of higher homologues from lower ones. The results suggest the possibility that the production mechanisms for hydrocarbons and carboxylic acids may be similar, and impose constraints on the identity of the reactant species.

  16. Cosmic rays interaction with comets and its impact on cometary isotopic and chemical composition

    NASA Astrophysics Data System (ADS)

    Gronoff, G.; Maggiolo, R.; Mertens, C. J.; Airapetian, V.; De Keyser, J.; Cessateur, G.; Dhooghe, F.; Gunell, H.

    2015-12-01

    Comets contain the most pristine material in the solar system. However, since their formation ~4.5 Gy ago, they have been altered by cosmic rays. The galactic and solar cosmic rays have a broad spectrum of energies and interact with the cometary surface and subsurface. While low energy cosmic rays interact only with the cometary surface, the most energetic cosmic rays deposit significant amount of energy down to tens of meters. This interaction can modify the isotopic ratio in cometary ices and create secondary compounds through radiolysis. We perform a theoretical analysis of the effect of cosmic rays on cometary material. We modeled the energy deposition of cosmic ray as a function of depth using a Geant4 applicationmodified to take into account the isotope creation process. We analyze the consequences of the energy deposition on the isotopic and chemical composition of cometary ices and discuss their implication on the interpretation of cometary observations.

  17. Boron-cycling by subducted lithosphere; insights from boron-isotope compositions of the Kokchetav tourmalines

    NASA Astrophysics Data System (ADS)

    Ota, T.; Kobayashi, K.; Moriguti, T.; Nakamura, E.

    2007-12-01

    For understanding the Earth's chemical evolution, the role of subducting plates has long been focused on. Stable isotopes can provide critical evidence to identify materials experienced geological processes near the surface. In this study, we examined B-isotope compositions of tourmalines from the Kokchetav diamondiferous UHP metamorphic belt, particularly a recently discovered high-K tourmaline from Kumdy-kol[1]. The high-K tourmaline occurs in Qtz-Kfs layers, alternating with Grt-Cpx-Bt-Qtz rocks. It has microdiamond- bearing and K-rich (K2O=~2.38 wt.%) cores, which yield heavy B-isotope ratios (δ11B=+3.2~+7.7, analyzed by SIMS). Our results suggest that the high-K tourmaline would be crystallized under high-pressure within the diamond stability from fluids or melts with the surficial B-isotope signature, which is clearly different from that of ordinary tourmalines (δ11B=-16.6~-2.3) experienced the isotope fractionation through subduction-related dehydration reactions. Tourmalines with heavy B-isotope ratios have been described from marine evaporites and carbonates[2]. The presence of silicate-carbonate melt inclusions with microdiamonds in metacarbonate rocks from Kumdy- kol[3] implies that the heavy B-isotope in the high-K tourmaline might have derived from the melt preserved in the metacarbonate rocks. However, recrystallized carbonates can yield light B-isotope ratios (δ11B=~-5[4]), and it is doubtful that carbonates could have retained the heavy B-isotope signature during subduction to the depths. The alternative source of the heavy B-isotope is serpentinite in hydrated lithospheric mantle, because serpentinized peridotites are enriched in heavy B-isotope (δ11B=+5.4~+25[5]). Serpentinization of subducting lithospheric mantle, with enrichment of heavy B-isotope, can be realized by transform faulting near oceanic ridges and normal faulting at trench-outer rise regions, followed by penetration of seawater into the lithospheric mantle prior to subduction[6

  18. Stable isotope study of a new chondrichthyan fauna (Kimmeridgian, Porrentruy, Swiss Jura): an unusual freshwater-influenced isotopic composition for the hybodont shark Asteracanthus

    NASA Astrophysics Data System (ADS)

    Leuzinger, L.; Kocsis, L.; Billon-Bruyat, J.-P.; Spezzaferri, S.; Vennemann, T.

    2015-12-01

    Chondrichthyan teeth (sharks, rays, and chimaeras) are mineralized in isotopic equilibrium with the surrounding water, and parameters such as water temperature and salinity can be inferred from the oxygen isotopic composition (δ18Op) of their bioapatite. We analysed a new chondrichthyan assemblage, as well as teeth from bony fish (Pycnodontiformes). All specimens are from Kimmeridgian coastal marine deposits of the Swiss Jura (vicinity of Porrentruy, Ajoie district, NW Switzerland). While the overall faunal composition and the isotopic composition of bony fish are generally consistent with marine conditions, unusually low δ18Op values were measured for the hybodont shark Asteracanthus. These values are also lower compared to previously published data from older European Jurassic localities. Additional analyses on material from Solothurn (Kimmeridgian, NW Switzerland) also have comparable, low-18O isotopic compositions for Asteracanthus. The data are hence interpreted to represent a so far unique, freshwater-influenced isotopic composition for this shark that is classically considered a marine genus. While reproduction in freshwater or brackish realms is established for other hybodonts, a similar behaviour for Asteracanthus is proposed here. Regular excursions into lower salinity waters can be linked to the age of the deposits and correspond to an ecological adaptation, most likely driven by the Kimmeridgian transgression and by the competition of the hybodont shark Asteracanthus with the rapidly diversifying neoselachians (modern sharks).

  19. Stable isotope study of a new chondrichthyan fauna (Kimmeridgian, Porrentruy, Swiss Jura): an unusual freshwater-influenced isotopic composition for the hybodont shark Asteracanthus

    NASA Astrophysics Data System (ADS)

    Leuzinger, L.; Kocsis, L.; Billon-Bruyat, J.-P.; Spezzaferri, S.; Vennemann, T.

    2015-08-01

    Chondrichthyan teeth (sharks, rays and chimaeras) are mineralised in isotopic equilibrium with the surrounding water, and parameters such as water temperature and salinity can be inferred from the oxygen isotopic composition (δ18Op) of their bioapatite. We analysed a new chondrichthyan assemblage, as well as teeth from bony fish (Pycnodontiformes). All specimens are from Kimmeridgian coastal marine deposits of the Swiss Jura (vicinity of Porrentruy, Ajoie district, NW Switzerland). While the overall faunal composition and the isotopic composition of bony fish are consistent with marine conditions, unusually low δ18Op values were measured for the hybodont shark Asteracanthus. These values are also lower compared to previously published data from older European Jurassic localities. Additional analyses on material from Solothurn (Kimmeridgian, NW Switzerland) also have comparable, low-18O isotopic compositions for Asteracanthus. The data are hence interpreted to represent a so far unique, freshwater-influenced isotopic composition for this shark that is classically considered as a marine genus. While reproduction in freshwater or brackish realms is established for other hybodonts, a similar behaviour for Asteracanthus is proposed here. Regular excursions into lower salinity waters can be linked to the age of the deposits and correspond to an ecological adaptation, most likely driven by the Kimmeridgian transgression and by the competition of the primitive shark Asteracanthus with the rapidly diversifying neoselachians (modern sharks).

  20. Experimental assessment of environmental influences on the stable isotopic composition of Daphnia pulicaria and their ephippia

    NASA Astrophysics Data System (ADS)

    Schilder, J.; Tellenbach, C.; Möst, M.; Spaak, P.; van Hardenbroek, M.; Wooller, M. J.; Heiri, O.

    2015-02-01

    The stable isotopic composition of fossil resting eggs (ephippia) of Daphnia spp. is being used to reconstruct past environmental conditions in lake ecosystems. However, the underlying assumption that the stable isotopic composition of the ephippia reflects the stable isotopic composition of the parent Daphnia, of their diet and of the environmental water have yet to be confirmed in a controlled experimental setting. We performed experiments with Daphnia pulicaria cultures, which included a control treatment conducted at 12 °C in filtered lake water and with a diet of fresh algae, and three treatments in which we manipulated the stable carbon isotopic composition (δ13C value) of the algae, stable oxygen isotopic composition (δ18O value) of the water, and the water temperature, respectively. The stable nitrogen isotopic composition (δ15N value) of the algae was similar for all treatments. At 12 °C, differences in algal δ13C values and in δ18O values of water are reflected in those of Daphnia. The differences between ephippia and Daphnia stable isotope ratios were similar in the different treatments (δ13C: + 0.2 ± 0.4‰ (SD); δ15N: -1.6 ± 0.4‰; δ18O: -0.9 ± 0.4‰) indicating that changes in dietary δ13C and δ18O values of water are passed on to these fossilizing structures. A higher water temperature (20 °C) resulted in lower δ13C values in Daphnia and ephippia than in the other treatments with the same food source and in a minor change in the difference between δ13C values of ephippia and Daphnia (to -1.3 ± 0.3‰). This may have been due to microbial processes or increased algal respiration rates in the experimental containers, which may not affect Daphnia in natural environments. There was no significant difference in the offset between δ18O and δ15N values of ephippia and Daphnia between the 12 °C and 20 °C treatments, but the δ18O values of Daphnia and ephippia were on average 1.2‰ lower at 20 °C compared with 12 °C. We conclude

  1. Lead isotopic compositions of common arsenical pesticides used in New England

    USGS Publications Warehouse

    Ayuso, Robert; Foley, Nora; Robinson, Gilpin; Wandless, Gregory; Dillingham, Jeremy

    2004-01-01

    The three most important arsenical pesticides and herbicides that were extensively used on apple, blueberry, and potato crops in New England from mid-1800s to recent times are lead arsenate, calcium arsenate, and sodium arsenate. Lead arsenate was probably the most heavily used of the arsenical pesticides until it was banned in 1988. Other metal-arsenic pesticides were also used but in lesser amounts. A recent report identified areas in New England where arsenical pesticides were used extensively (Robinson and Ayuso, 2004). On the basis of factor analysis of metal concentrations in stream sediment samples, a positive correlation with pesticide use was shown in regions having stream sediment sample populations that contained concentrations of high arsenic and lead. Lead isotope compositions of stream sediments from areas with heavy use of the pesticides could not be entirely explained by lead originating from rock sulfides and their weathering products. An industrial lead contribution (mostly from atmospheric deposition of lead) was suggested in general to explain the lead isotopic distributions of the stream sediments that could not be accounted for by the natural lead in the environment. We concluded that when agricultural land previously contaminated with arsenical pesticides is urbanized, pesticide residues in the soils and stream sediments could be released into the groundwater. No lead isotopic data characterizing the compositions of pesticides were available for comparison. We have determined the lead isotopic compositions of commonly used pesticides in New England, such as lead arsenate, sodium metaarsenite, and calcium arsenate, in order to assist in future isotopic comparisons and to better establish anthropogenic sources of Pb and As. New data are also presented for copper acetoarsenite (or Paris green), methyl arsonic acid and methane arsonic acid, as well as for arsanilic acid, all of which are used as feed additives to promote swine and poultry growth

  2. Cosmic Ray Exposure Modification of the Molybdenum Isotopic Composition of Iron Meteorites

    NASA Astrophysics Data System (ADS)

    Worsham, E. A.; Bermingham, K. R.; Walker, R. J.

    2015-12-01

    Accurate grouping of meteorites that represent specific planetary bodies is paramount to understanding early planetary processes, such as accretion and differentiation. Most iron meteorite groups represent the cores of differentiated planetesimals, and therefore hold insights into the timing and mechanisms of core formation and crystallization. Molybdenum isotopic compositions have been shown to vary between meteorite groups due to nucleosynthetic heterogeneities, and, thus, can be used as a genetic tracer [1]. Where isotopic differences can be resolved among iron meteorites purported to be from the same group, it is possible to reject genetic linkages. However, implicit in the use of Mo as a genetic tracer is the assumption of intra-group homogeneity, which does not hold true for Os isotopes, for example [2]. High neutron fluence due to cosmic ray exposure (CRE) has been shown to modify Os isotopic compositions [2]. We report deviations of 95Mo, normalized to 98Mo/96Mo to correct for instrumental mass bias, between iron meteorites of the same group. For instance, in group IVB, Tlacotepec has a 95Mo/96Mo ratio that is ~30 ppm lower than that of most other IVB iron meteorites. Molybdenum-95 is correlated with 189Os and 190Os in each of the three iron meteorite groups examined here, indicating that Mo isotopes are also modified by CRE. Because 95Mo has the largest neutron capture cross section and resonance integral of the Mo isotopes, the likely nuclear reaction is: 95Mo(n,γ)96Mo. The correlation between 95Mo and 189Os or 190Os can be used to correct the Mo isotopes to a pre-exposure composition, as has been done for W isotopes [e.g., 3]. The pre-exposure 95Mo for the IAB complex, IVB, and IIIAB iron meteorite groups is calculated as the y-intercept of each of the slopes defined by the correlation of 95Mo with 189Os. [1] Dauphas et al. (2002) Astrophys. J. 565, 640-644. [2] Walker (2012) EPSL 351-352, 36-44. [3] Wittig et al. (2013) EPSL 361, 152-161.

  3. Soil Drying Effects on the Carbon Isotope Composition of Soil Respiration

    NASA Astrophysics Data System (ADS)

    Phillips, C. L.; Nickerson, N.; Risk, D.; Kayler, Z. E.; Rugh, W.; Mix, A. C.; Bond, B. J.

    2008-12-01

    Stable isotopes are used widely as a tool for determining sources of carbon (C) fluxes in ecosystem C studies. Environmental factors that change over time, such as moisture, can create dynamic changes in the isotopic composition of C assimilated by plants, and offers a unique opportunity to distinguish fast- responding plant C from slower-responding soil C pools, which under steady-state conditions may be too similar isotopically to partition. Monitoring the isotopic composition of soil respiration over a period of changing moisture conditions is potentially a useful approach for characterizing plant contributions to soil respiration. But this partitioning hinges on the assumption that any change in the isotopic signature of soil respiration is solely due to recent photosynthetic discrimination, and that post-photosynthetic processes, such as microbial respiration, do not discriminate as moisture decreases. The purpose of the present study is to test the assumption that δ13CO2 from microbial respiration remains static as soil dries. We conducted a series of greenhouse experiments employing different techniques to isolate microbial respiration from root respiration. The first involves removing roots from soil, and showed that when roots are present, respiration from dry soil is enriched in 13C relative to moist soil, but when roots are absent, respiration is isotopically similar from moist and dry soils. This indicates that rhizospheric respiration changes isotopically with moisture whereas soil microbial respiration does not. In contrast, a second experiment in which soil columns without plants were monitored as they dried, showed respiration from very dry soil to be enriched by 8‰ relative to moist soil. However, simulations with an isotopologue-based soil gas diffusion model demonstrate that at least a portion of the apparent enrichment is due to non-steady state gas transport processes. Careful sampling methodologies which prevent or account for non

  4. The Sulfur Isotope Composition of the Pyrite Burial Flux in the Modern Ocean

    NASA Astrophysics Data System (ADS)

    Turchyn, A. V.; Antler, G.; Byrne, D. J.; Sun, X.

    2014-12-01

    Microbial sulfate reduction followed by sulfide mineral burial, typically as pyrite, represents the largest removal pathway for sulfur from the exogenic sulfur reservoir. During microbial sulfate reduction, sulfur isotopes are partitioned such that the lighter 32S isotope is preferentially reduced; the magnitude of this partitioning has a large range (0 to 72‰), and therefore the average sulfur isotope composition of the global pyrite burial flux remains enigmatic. Recent work has mapped the global spatial distribution of microbial sulfate reduction rates in the modern ocean, which allows conclusions to be drawn concerning the conditions and controls on where sulfate respiration occurs (Bowles et al., 2014). The local rate of sulfate reduction in a particular sediment column can be calculated by the change in sulfate concentrations in pore fluids below the surface, which yields the net flux of sulfate into marine sediments. A flux of sulfate into the sediment is assumed to be due to diffusion along a concentration gradient set up by the consumption of sulfate at depth. We have calculated the deep-sea rates of microbial sulfate reduction using over 700 drilling sites and arrive at a similar estimate of the global modern rate of sulfate respiration. Rates of sulfate reduction are not, however, the same as the rates of pyrite burial, which is likely limited to the uppermost sediments where reactive iron may be available, or in the most nearshore environments where the terrestrial supply of iron is high and rates of sulfate reduction are orders of magnitude higher than those in the deep-sea. Sulfur isotope fractionation during microbial sulfate reduction is a function of several environmental factors, including the rate of sulfate reduction. We use a new compilation of the link between sulfate reduction rate and sulfur isotope fractionation with a model of pyrite burial in a range of modern marine sediments to derive an estimate of the global pyrite burial flux and

  5. Chemical and sulfur isotopic composition of precipitation in Beijing, China.

    PubMed

    Zhu, Guangxu; Guo, Qingjun; Chen, Tongbin; Lang, Yunchao; Peters, Marc; Tian, Liyan; Zhang, Hanzhi; Wang, Chunyu

    2016-03-01

    China is experiencing serious acid rain contamination, with Beijing among the worst-hit areas. To understand the chemical feature and the origin of inorganic ions in precipitation of Beijing, 128 precipitation samples were collected and analyzed for major water-soluble ions and δ(34)S. The pH values ranged from 3.68 to 7.81 and showed a volume weighted average value (VWA) of 5.02, with a frequency of acid rain of 26.8 %. The VWA value of electrical conductivity (EC) was 68.6 μS/cm, which was nearly 4 times higher than the background value of northern China. Ca(2+) represented the main cation; SO4 (2-) and NO3 (-) were the dominant anion in precipitation. Our study showed that SO4 (2-) and NO3 (-) originated from coal and fossil fuel combustion; Ca(2+), Mg(2+), and K(+) were from the continental sources. The δ(34)S value of SO4 (2-) in precipitation ranged from +2.1 to +12.8‰ with an average value of +4.7‰. The δ(34)S value showed a winter maximum and a summer minimum tendency, which was mainly associated with temperature-dependent isotope equilibrium fractionation as well as combustion of coal with relatively positive δ(34)S values in winter. Moreover, the δ(34)S values revealed that atmospheric sulfur in Beijing are mainly correlated to coal burning and traffic emission; coal combustion constituted a significant fraction of the SO4 (2-) in winter precipitation.

  6. Fe and O isotope composition of meteorite fusion crusts: Possible natural analogues to chondrule formation?

    NASA Astrophysics Data System (ADS)

    Hezel, Dominik C.; Poole, Graeme M.; Hoyes, Jack; Coles, Barry J.; Unsworth, Catherine; Albrecht, Nina; Smith, Caroline; RehkäMper, Mark; Pack, Andreas; Genge, Matthew; Russell, Sara S.

    2015-02-01

    Meteorite fusion crust formation is a brief event in a high-temperature (2000-12,000 K) and high-pressure (2-5 MPa) regime. We studied fusion crusts and bulk samples of 10 ordinary chondrite falls and 10 ordinary chondrite finds. The fusion crusts show a typical layering and most contain vesicles. All fusion crusts are enriched in heavy Fe isotopes, with δ56Fe values up to +0.35‰ relative to the solar system mean. On average, the δ56Fe of fusion crusts from finds is +0.23‰, which is 0.08‰ higher than the average from falls (+0.15‰). Higher δ56Fe in fusion crusts of finds correlate with bulk chondrite enrichments in mobile elements such as Ba and Sr. The δ56Fe signature of meteorite fusion crusts was produced by two processes (1) evaporation during atmospheric entry and (2) terrestrial weathering. Fusion crusts have either the same or higher δ18O (0.9-1.5‰) than their host chondrites, and the same is true for Δ17O. The differences in bulk chondrite and fusion crust oxygen isotope composition are explained by exchange of oxygen between the molten surface of the meteorites with the atmosphere and weathering. Meteorite fusion crust formation is qualitatively similar to conditions of chondrule formation. Therefore, fusion crusts may, at least to some extent, serve as a natural analogue to chondrule formation processes. Meteorite fusion crust and chondrules exhibit a similar extent of Fe isotope fractionation, supporting the idea that the Fe isotope signature of chondrules was established in a high-pressure environment that prevented large isotope fractionations. The exchange of O between a chondrule melt and an 16O-poor nebula as the cause for the observed nonmass dependent O isotope compositions in chondrules is supported by the same process, although to a much lower extent, in meteorite fusion crusts.

  7. Record of seasonal body fluid composition in Black Clam (Bivalve) using clumped isotope thermometric approach

    NASA Astrophysics Data System (ADS)

    Rahman, H.; Naidu, P. K.; Ghosh, P.

    2012-12-01

    Application of clumped isotope thermometry (Ghosh et al., 2006) is highly debated while resolving the issue of kinetic effect during biogenic carbonate precipitation. Mollusks are particularly attractive target to study the kinetic effect (Eiler, 2011) in the biological system owing to its incremental growth ring patterns. This allows understanding the role of environmental parameters other than temperature driving the distribution of heavier isotopologues. Guo et al., (2010) indicated role of pH in driving the distribution of heavier isotopolgues in the carbonates. We investigated here clumped isotopic composition of Black Calm (bivalve shell) caught live from a location in Southern Indian Estuary. The region experiences large change in seasonal condition. The physical environmental parameters at that location were monitored for last 3 years at monthly interval. The salinity, temperature, pH information are available for all the months when mollusc growth bands are deposited. The bottom water of estuary, where bivalve thrives experience maximum temperature of 32°C during November and December, while temperature during Monsoon months (July, August) drops lows to 26°C. Initial results on clumped isotope thermometry on the growth bands precipitated suggests that during the time in a year when pH level is alkaline i.e. 8.0±0.2 there is large consistency between actual temperature and estimated temperature using clumped isotope based thermometry. While the pH drops towards acidic i.e. 6.8±0.1 lower temperature estimates compared to actual was recorded. The effect of metabolic rate and body temperature variability is not been investigated as suggested in case of land snails based clumped isotope thermometry (Zaarur et al., 2011). Mollusc shell can be used to trace the composition of environmental water while pH variation is minimal. In this presentation analyses of more shell specimen and explore the role of pH and osmo-regulation in mollusc determining the clumped

  8. Diamond growth history from in situ measurement of Pb and S isotopic compositions of sulfide inclusions

    NASA Astrophysics Data System (ADS)

    Rudnick, Roberta L.; Eldridge, C. Stewart; Bulanova, Galina P.

    1993-01-01

    In a continuing effort to understand crust-mantle dynamics, we have determined the S and Pb isotopic compositions of mantle sulfides encapsulated within diamonds from under the Siberian craton and compared these results to those of previously investigated African counterparts. Because diamond inclusions are isolated from exchange with surrounding mantle, they may preserve the history of diamond growth and act as direct tracers of the origins of mantle materials. Study of these inclusions may thus offer the best chance of recognizing global-scale interaction between Earth's crust and mantle. Although δ34S values of the Siberian sulfides do not deviate significantly from the mantle value of 0‰ ± 3‰, Pb isotopic compositions are highly variable. Pb isotopic compositions of sulfides from peridotitic suite diamonds generally plot near the terrestrial Pb growth curve, with model ages ranging between 0 and 2 Ga, whereas sulfides from eclogitic suite diamonds have radiogenic compositions, plotting beyond the growth curve. These results, which are similar to those for sulfides in African diamonds, suggest that the sulfides from eclogitic suite diamonds were derived from a source with an unusually high U/Pb ratio and may indicate a common process (such as subduction of crystal materials into the mantle) operating beneath Africa and Siberia. The absence of extremely radiogenic Pb in sulfides from eclogite xenoliths suggests that the radiogenic material from which eclogitic suite diamonds grew was a transient feature of the mantle, associated with diamond growth. The ultimate origin of this high U/Pb signature, however, remains enigmatic. Large variations in Pb isotopic composition of sulfides from different zones in a single peridotitic suite diamond document (1) crystallization of the diamond's core near 2.0 Ga, (2) growth of its outer zone in an environment with a high U/Pb ratio similar to the growth environment of eclogitic suite diamonds, and (3) growth of the

  9. Strontium isotope composition of skeletal material can determine the birth place and geographic mobility of humans and animals.

    PubMed

    Beard, B L; Johnson, C M

    2000-09-01

    The Sr isotope composition measured in skeletal elements (e.g., bone, teeth, or antlers) can be used to infer the geographic region that an animal or human inhabited, because different regions tend to have distinct Sr isotope compositions, and natural variations in the relative abundance of Sr isotopes are not changed as Sr is processed through the food chain. Therefore, an organism that ingests Sr from one region can have a Sr isotope composition that is different than that of an organism that ingests Sr from another region. The Sr isotope composition of skeletal elements is a reflection of the concentration-weighted average of dietary Sr that was ingested while that skeletal element was produced. Because different skeletal elements grow and exchange Sr at different stages during the life times of organisms, Sr isotope analysis of different skeletal elements can be used to infer changes in geographic location at different stages in an organism's life. The Sr isotope composition measured in human teeth will reflect the average Sr isotope composition that was ingested as a child, due to the immobile nature of Sr and Ca in teeth after formation, whereas the Sr isotope composition of bone will reflect the average isotopic composition over the last ten years of life, due to continuous biological processing of Sr and Ca in bone. Inferring the average isotopic composition of dietary Sr is best done by analyzing skeletal fragments from control groups, which might be animals that have the same feeding habits as the animal in question, or, in the case of humans, analysis of close family relatives. In cases where it is not possible to construct a Sr isotope database from control groups, it becomes necessary to estimate the isotopic composition of dietary Sr based on geologic principles. We present three case studies from our research that illustrate a range of approaches: (1) results from a criminal case where a deer was illegally harvested and the location of the deer was

  10. Measurement of the oxygen isotopic composition of nitrate in seawater and freshwater using the denitrifier method

    USGS Publications Warehouse

    Casciotti, K.L.; Sigman, D.M.; Hastings, M. Galanter; Böhlke, J.K.; Hilkert, A.

    2002-01-01

    We report a novel method for measurement of the oxygen isotopic composition (18O/16O) of nitrate (NO3-) from both seawater and freshwater. The denitrifier method, based on the isotope ratio analysis of nitrous oxide generated from sample nitrate by cultured denitrifying bacteria, has been described elsewhere for its use in nitrogen isotope ratio (15N/14N) analysis of nitrate.1Here, we address the additional issues associated with 18O/16O analysis of nitrate by this approach, which include (1) the oxygen isotopic difference between the nitrate sample and the N2O analyte due to isotopic fractionation associated with the loss of oxygen atoms from nitrate and (2) the exchange of oxygen atoms with water during the conversion of nitrate to N2O. Experiments with 18O-labeled water indicate that water exchange contributes less than 10%, and frequently less than 3%, of the oxygen atoms in the N2O product for Pseudomonas aureofaciens. In addition, both oxygen isotope fractionation and oxygen atom exchange are consistent within a given batch of analyses. The analysis of appropriate isotopic reference materials can thus be used to correct the measured 18O/16O ratios of samples for both effects. This is the first method tested for 18O/16O analysis of nitrate in seawater. Benefits of this method, relative to published freshwater methods, include higher sensitivity (tested down to 10 nmol and 1 μM NO3-), lack of interference by other solutes, and ease of sample preparation.

  11. Sulfide isotopic compositions in shergottites and ALH84001, and possible implications for life on Mars

    SciTech Connect

    Greenwood, J.P.; McSween, H.Y. Jr.; Riciputi, L.R.

    1997-10-01

    The shergottite and ALH84001 meteorites hold keys for understanding geologic and possibly biologic processes on Mars. Recently, it has been proposed that carbonates in ALH84001, and the Fe-sulfides they contain, are products of extraterrestrial biogenic activity. Here we report ion microprobe analyses of sulfides in shergottites and ALH84001. The sulfur isotope ratios of igneous pyrrhotites in shergottites (mean {delta}{sup 34}S{sub CDT}: Shergotty = -0.4{per_thousand}, Zagami = +2.7{per_thousand}, EETA79001A = 1.9{per_thousand}, EETA79001B = -1.7{per_thousand}, LEW88516 = -1.9{per_thousand}, QUE94201 = +0.8{per_thousand}) are similar to those of terrestrial ocean-floor basalts, suggesting that the sulfur isotopic composition of the Martian mantle may be similar to that of the mantle of the Earth. The sulfur isotopic systematics of ALH84001 sulfides are distinct from the shergottites. Measured sulfur isotope ratios of eight pyrite grains ({delta}{sup 34}S{sub CDT} = +2.0 to +7.3{per_thousand}) in crushed zones confirm previously reported analyses of isotopically heavy sulfides and are indistinguishable from an Fe-sulfide zone within a carbonate globule ({delta}{sup 34}S{sub CDT} = +6.0{per_thousand}). Analyses of synthesized, fine-grained mixtures of sulfide, carbonate, and magnetite indicate than the measured sulfur isotope ratio is independent of the presence of carbonate and magnetite in the sputtered volume, confirming the accuracy of the analysis of the fine-grained sulfide in the carbonate globule. Terrestrial biogenic sulfate reduction typically results in light isotopic enrichments. The similarity of {delta}{sup 34}S values of the sulfides in ALH84001 imply that the Fe-sulfide zones within ALH84001 carbonates are probably not the result of bacterial reduction of sulfate. 38 refs., 3 figs., 1 tab.

  12. Neoproterozoic variations in the C-isotopic composition of seawater: stratigraphic and biogeochemical implications

    NASA Technical Reports Server (NTRS)

    Kaufman, A. J.; Knoll, A. H.

    1995-01-01

    The recent proliferation of stratigraphic studies of delta 13C variation in carbonates and organic C in later Neoproterozoic and basal Cambrian successions (approximately 850-530 Ma) indicates a strong oscillating trend in the C-isotopic composition of surface seawater. Alone, this trend does not adequately characterize discrete intervals in Neoproterozoic time. However, integrated with the vectorial signals provided by fossils and Sr-isotopic variations, C isotope chemostratigraphy facilitates the interbasinal correlation of later Neoproterozoic successions. Results of these studies are evaluated in terms of four stratigraphic intervals: (1) the Precambrian/Cambrian boundary, (2) the post-Varanger terminal Proterozoic, (3) the late Cryogenian, and (4) the early Cryogenian. Where biostratigraphic or radiometric data constrain the age of Neoproterozoic sedimentary sequences, secular variations in C and Sr isotopes can provide a level of stratigraphic resolution exceeding that provided by fossils alone. Isotopic data place strong constraints on the chemical evolution of seawater, linking it to major tectonic and paleoclimatic events. They also provide a biogeochemical framework for the understanding of the initial radiation of macroscopic metazoans, which is associated stratigraphically, and perhaps causally, with a global increase in the burial of organic C and a concomitant rise of atmospheric O2.

  13. Effect of storage on the isotopic composition of nitrate in bulk precipitation.

    PubMed

    Spoelstra, John; Schiff, Sherry L; Jeffries, Dean S; Semkin, Ray G

    2004-09-15

    Stable isotopic analysis of atmospheric nitrate is increasingly employed to study nitrate sources and transformations in forested catchments. Large volumes have typically been required for delta18O and delta15N analysis of nitrate in precipitation due to relatively low nitrate concentrations. Having bulk collectors accumulate precipitation over an extended time period allows for collection of the required volume as well as reducing the total number of analyses needed to determine the isotopic composition of mean annual nitrate deposition. However, unfiltered precipitation left in collectors might be subject to microbial reactions that can alter the isotopic signature of nitrate in the sample. Precipitation obtained from the Turkey Lakes Watershed was incubated under conditions designed to mimic unfiltered storage in bulk precipitation collectors and monitored for changes in nitrate concentration, delta15N, and delta18O. Results of this experiment indicated that no detectable nitrate production or assimilation occurred in the samples during a two-week incubation period and that atmospheric nitrate isotopic ratios were preserved. The ability to collect unfiltered precipitation samples for an extended duration without alteration of nitrate isotope ratios is particularly useful at remote study sites where daily retrieval of samples may not be feasible.

  14. Stable isotope composition of precipitation in the south and north slopes of Wushaoling Mountain, northwestern China

    NASA Astrophysics Data System (ADS)

    Zongxing, Li; Qi, Feng; Song, Yong; Wang, Q. J.; Yang, Jiao; Yongge, Li; Jianguo, Li; Xiaoyan, Guo

    2016-12-01

    A study of spatial and temporal variability of precipitation isotope composition on the southern and north slopes of Wushaoling Mountain was conducted in order to explore the processes influencing its evolution. The analysis indicated that the isotopic composition, the slopes and intercepts of Local Meteroic Water Lines, altitude gradients and temperature effect are higher on the north slope than those on the south slope. The d-excess showed an increase from lower to higher altitudes, and the altitude gradients changed with season. The correlation coefficients between δ18O and d-excess decreased with increasing altitude due to weakening sub-cloud evaporation. Westerly wind principally dominates Wushaoling Mountain, so the relatively negative stable isotope values observed are related to the long distance transportation of water vapor in spring and winter. In summer and autumn, the locally strong sub-cloud evaporation cause relatively higher δ18O and lower d-excess. The results suggested that the sub-cloud evaporation has enriched the δ18O composition by 23%, 23%, 32%, 42% and 29% in May, June, July, August and September, respectively. In some circumstances, δ18O and δD were depleted at the end of multi-days rainfall events due to the rainout process. In addition, monsoonal moisture caused some negative δ18O in summer when an enhanced cyclonic circulation had developed on Tibetan Plateau. The study enhances the knowledge of isotopic evolution of precipitation and provides a basis for further study of isotopic hydrology in arid regions.

  15. Anthropogenic Pb input into Bohai Bay, China: Evidence from stable Pb isotopic compositions in sediments

    NASA Astrophysics Data System (ADS)

    Hu, Ningjing; Huang, Peng

    2016-04-01

    Anthropogenic Pb input into Bohai Bay, China: Evidence from stable Pb isotopic compositions in sediments Hu Ning-jinga, Huang Pengb,, Liu Ji-huaa, a First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China b Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China To investigate the source of Pb within Bohai Bay, Pb concentrations and Pb isotopic compositions (204Pb, 206Pb, 207Pb, and 208Pb) of surface sediments in this area were determined. The Pb concentration in this bay varied widely from 6.9 to 39.2 μg/g (average: 21.8 ± 7.8 μg/g), and the Pb isotopic compositions ranged from 0.8338 to 0.8864 (average: 2.0997 ± 0.0180) for 208Pb/206Pb and from 2.0797 to 2.1531 (average: 0.8477 ± 0.0135) for 207Pb/206Pb, presenting in three distinct clusters. The Pb isotopic ratios of sediments from the northeastern (NE zone) and northwestern (NW zone) coastal areas were significantly influenced by anthropogenic sources such as coal combustion and automobile emission. In sediments from the central and southern Bohai Bay (C-S zone); however, Pb mainly originated from the Yellow River catchment, as a result of lithogenic sediment (from rock weathering) accumulation. The Pb isotopic ratios further indicate that, apart from riverine inputs, the neighboring large-scale ports and aerosols significantly contributed to the anthropogenic Pb contained in these sediments. Pb contamination in the Haihe and Luanhe river mouths as well as in the regions near ports is also suggested from anthropogenic enrichment factors. As cities and ports continue to develop around Bohai Bay, a long-term extensive sewage monitoring program is highly recommended.

  16. Stable isotope composition of land snail body water and its relation to environmental waters and shell carbonate

    NASA Astrophysics Data System (ADS)

    Goodfriend, Glenn A.; Magaritz, Mordeckai; Gat, Joel R.

    1989-12-01

    Day-to-day and within-day (diel) variations in δD and δ18O of the body water of the land snail, Theba pisana, were studied at a site in the southern coastal plain of Israel. Three phases of variation, which relate to isotopic changes in atmospheric water vapor, were distinguished: 1) on rain days, snail water becomes isotopically depleted approximately in the direction of the rain isotope values, but always less depleted in D as is atmospheric water vapor; 2) during the 1-3 days following a rain, the snail water becomes isotopically enriched along a line with slope < 8, in δD vs. δ18O space (this relates to an increasing influence of humidity derived from the Mediterranean Sea); 3) a period of relative stability of the isotopic composition persists until the next rain event. The isotopic variations can be explained by isotopic equilibration with atmospheric water vapor and/or uptake of dew derived therefrom. During the winter, when the snails are active, there is only very minor enrichment in 18O relative to equilibrium with water vapor or dew, apparently as a result of metabolic activity. But this enrichment becomes pronounced after long periods of inactivity. Within-day variation in body water isotopic composition is minor on non-rain days. Shell carbonate is enriched in 18O by ca. 1-2%. relative to equilibrium with body water. In most regions, the isotopic composition of atmospheric water vapor (or dew) is a direct function of that of rain. Because the isotopic composition of snail body water is related to that of atmospheric water vapor and the isotopic composition of shell carbonate in turn is related to that of body water, land snail shell carbonate 18O should provide a reliable indication of rainfall 18O. However, local environmental conditions and the ecological properties of the snail species must be taken into account.

  17. Reconstructing Cambro-Ordovician Seawater Composition using Clumped Isotope Paleothermometry on Calcitic and Phosphatic Brachiopods

    NASA Astrophysics Data System (ADS)

    Bergmann, K.; Robles, M.; Finnegan, S.; Hughes, N. C.; Eiler, J. M.; Fischer, W. W.

    2012-12-01

    A secular increase in δ18O values of marine fossils through early Phanerozoic time raises questions about the evolution of climate and the water cycle. This pattern suggests two end-member hypotheses 1) surface temperatures during early Paleozoic time were very warm, in excess of 40°C (tropical MAT), or 2) the isotopic composition of seawater increased by up to 7-8‰. It has been difficult to evaluate these hypotheses because the δ18O composition of fossils depends on both temperature and the δ18O of water. Furthermore, primary isotopic signatures can be overprinted by diagenetic processes that modify geological materials. This too could explain the decrease in δ18O values of marine fossils with age. Carbonate clumped isotope thermometry can constrain this problem by providing an independent measure of crystallization temperature and, when paired with classical δ18O paleothermometry, can determine the isotopic composition of the fluid the mineral last equilibrated with. Combined with traditional tools, this method has the potential to untangle primary isotopic signatures from diagenetic signals. We measured the isotopic ordering of CO3 groups (Δ47) substituted into the phosphate lattice of phosphatic brachiopods in Cambrian strata. Phosphatic fossils are generally less soluble than carbonates in surface and diagenetic environments, and so are hypothesized to provide a more robust record of primary growth conditions. They also provide an archive prior to the rise of thick shelled calcitic fossils during the Ordovician Radiation. Additionally, measurements of the δ18O of the CO3 groups can be compared with the δ18O of PO4 groups to test whether their mutual fractionation is consistent with primary growth and the apparent temperature recorded by carbonate clumped isotope measurements. We are constructing a phosphatic brachiopod calibration for carbonate clumped isotope thermometry, and Δ47 values of CO2 extracted from modern phosphatic brachiopods suggest

  18. Anthropogenic Pb input into Bohai Bay, China: Evidence from stable Pb isotopic compositions in sediments

    NASA Astrophysics Data System (ADS)

    Ning-jing, Hu; Peng, Huang; Hui, Zhang; Ai-mei, Zhu; Ji-hua, Liu; Jun, Zhang; Lian-hua, He

    2015-10-01

    To investigate the source of Pb within Bohai Bay, Pb concentrations and Pb isotopic compositions (204Pb, 206Pb, 207Pb, and 208Pb) of surface sediments in this area were determined. The Pb concentration in this bay varied widely from 6.9 to 39.2 μg/g (average: 21.8±7.8 μg/g), and the Pb isotopic compositions ranged from 0.8338 to 0.8864 (average: 2.0997±0.0180) for 208Pb/206Pb and from 2.0797 to 2.1531 (average: 0.8477±0.0135) for 207Pb/206Pb, presenting in three distinct clusters. The Pb isotopic ratios of sediments from the northeastern (NE zone) and northwestern (NW zone) coastal areas were significantly influenced by anthropogenic sources such as coal combustion and automobile emission. In sediments from the central and southern Bohai Bay (C-S zone); however, Pb mainly originated from the Yellow River catchment, as a result of lithogenic sediment (from rock weathering) accumulation. The Pb isotopic ratios further indicate that, apart from riverine inputs, the neighboring large-scale ports and aerosols significantly contributed to the anthropogenic Pb contained in these sediments. Pb contamination in the Haihe and Luanhe river mouths as well as in the regions near ports is also suggested from anthropogenic enrichment factors. As cities and ports continue to develop around Bohai Bay, a long-term extensive sewage monitoring program is highly recommended.

  19. Lead isotope and trace element composition of urban soils in Mongolia

    NASA Astrophysics Data System (ADS)

    Tserenpil, Sh.; Sapkota, A.; Liu, C.-Q.; Peng, J.-H.; Liu, B.; Segebade, P. Chr.

    2016-08-01

    Lead (Pb) pollution in and around Ulaanbaatar is of national concern, given that the Mongolian capital is home to nearly half of the country's entire population. By comparison, Mongolian countryside is a pristine environment because of its sparse population and low industrial activity. The concentration of Pb in urban soils (average of 39.1 mg kg-1) was twice the values found (average 18.6 mg kg-1) in background territories (i.e., Mongolian rural sites). Furthermore, Pb contamination was examined by using Pb stable isotopic composition, and covariance of Pb isotopic ratios showed two groups between rural and urban soils as pristine and disturbed sites. The 206Pb/207Pb ratio, the most prominent fingerprint for Pb pollution, was 1.163-1.185 for the urban whereas values for rural soils (1.186-1.207) were analogue to the regional Pb isotopic signatures. Local coal sources and their combustion products, one of the potential Pb pollution sources in Ulaanbaatar, have significant radiogenic properties in terms of Pb isotopic composition and revealed an average of 1.25 for 206Pb/207Pb and 19.551 for 206Pb/204Pb ratios. Thus, contributions from coal firing activity to Pb pollution lower than it was assumed, and smaller range of these values measured in urban soils may be attributed to the mixing of less radiogenic Pb as a constituent of the leaded gasolines.

  20. The Impact of Fe(II) on NO2- Isotopic Composition During Denitrification by Natural Sediment

    NASA Astrophysics Data System (ADS)

    Diaz-Etchevehere, D.; Wankel, S. D.

    2015-12-01

    The role of Fe(II) on Nitrite (NO2-) isotopic composition during denitrification was investigated in anaerobic, closed-system batch incubations of tidal marsh sediments. Fe(II) is often found in similar redox conditions and can rapidly reduce NO2- to N2 and/or nitrous oxide (N2O), a potent greenhouse gas, through a process called chemodenitrification. Microbial communities can also reduce nitrate (NO3-) to NO2- and eventually to N2O through the anaerobic process of biological denitrification. This study compared the impact on NO2- accumulation when Fe(III)-containing minerals ferrihydrite and goethite were added to natural sediments. The presence of dissolved Fe(II), presumably produced by microbial iron reduction, significantly limited the amount of NO2- accumulation, suggesting that Fe(II) may have chemically reduced NO2-. Changes in the δ15N of the intermediate NO2- pool in each bottle was measured, but the apparent isotope effects of NO2- reduction were indistinguishable among treatments, suggesting that the reaction of Fe(II) and NO2- imparts an isotope effect on the NO2- pool of a similar magnitude to that of biological NO2- reduction. The isotopic composition of N2O and its 15N site preference will be measured to determine if chemodenitrification truly occurred, and if so, the relative contributions to N2O production from biological denitrification and chemodenitrification will be determined.

  1. New views on the isotopic composition of atmospheric oxygen

    NASA Astrophysics Data System (ADS)

    Luz, B.

    2001-05-01

    Air oxygen is enriched in O-18 with respect to ocean water by about 23 permil. This enrichment is named "Dole effect" after its discoverer. Air oxygen originates from marine and terrestrial photosynthesis that produces oxygen gas without fractionation with respect to the substrate water. The O-18 enrichment results primarily from preferential removal of O-16 during respiratory uptake. However, the discrimination against O-18 in ordinary dark respiration is only 18 permil, and cannot account for the entire magnitude of the Dole effect. Part of the discrepancy may be explained by enrichment of the substrate water in terrestrial evapo-transpiration. But the existing evidence on the magnitude of this enrichment shows that this mechanism alone cannot explain the discrepancy. In an attempt to better understand the Dole effect we have studied the overall fractionation in soil and aquatic oxygen uptake. Due to slow gas diffusion in soils and roots the discrimination is smaller than in respiration. This result thus increases the discrepancy. On the other hand, our new estimates show that discrimination in aquatic oxygen uptake is considerably greater than previously assumed. Oxygen uptake in the surface waters of oceans and lakes takes place by ordinary dark respiration as well as by cyanide resistant respiration in both dark and light conditions, and by photorespiration and Mehler reaction that occur only during illumination. Thus in order to study the overall discrimination in aquatic systems it is necessary to evaluate its effects in both light and dark conditions and to separate the effect of photosynthetic production of oxygen. Such separation is possible if gross rates of oxygen production and consumption are known. We have estimated these rates from in situ incubation experiments and from the natural distribution of O-16, O-17, O-18 and the ratio of dissolved oxygen/argon. We have used isotopic and elemental budgets to derive the overall respiratory fractionation in

  2. Hydrogen isotope composition of leaf wax n-alkanes in Arabidopsis lines with different transpiration rates

    NASA Astrophysics Data System (ADS)

    Pedentchouk, N.; Lawson, T.; Eley, Y.; McAusland, L.

    2012-04-01

    Stable isotopic compositions of oxygen and hydrogen are used widely to investigate modern and ancient water cycles. The D/H composition of organic compounds derived from terrestrial plants has recently attracted significant attention as a proxy for palaeohydrology. However, the role of various plant physiological and biochemical factors in controlling the D/H signature of leaf wax lipids in extant plants remains unclear. The focus of this study is to investigate the effect of plant transpiration on the D/H composition of n-alkanes in terrestrial plants. This experiment includes 4 varieties of Arabidopsis thaliana that differ with respect to stomatal density and stomatal geometry. All 4 varieties were grown indoors under identical temperature, relative humidity, light and watering regimes and then sampled for leaf wax and leaf water stable isotopic measurements. During growth, stomatal conductance to carbon dioxide and water vapour were also determined. We found that the plants varied significantly in terms of their transpiration rates. Transpiration rates were significantly higher in Arabidopsis ost1 and ost1-1 varieties (2.4 and 3.2 mmol m-2 s-1, respectively) than in Arabidopsis RbohD and Col-0 (1.5 and 1.4). However, hydrogen isotope measurements of n-alkanes extracted from leaf waxes revealed a very different pattern. Varieties ost1, ost1-1, and RbohD have very similar deltaD values of n-C29 alkane (-125, -128, and -127 per mil), whereas the deltaD value of Col-0 is more negative (-137 per mil). The initial results of this work suggest that plant transpiration is decoupled from the D/H composition of n-alkanes. In other words, physical processes that affect water vapour movement between the plant and its environment apparently cannot account for the stable hydrogen isotope composition of organic compounds that comprise leaf waxes. Additional, perhaps biochemical, processes that affect hydrogen isotope fractionation during photosynthesis might need to be invoked

  3. Lead Isotopic Compositions of the Endeavour Sulfides, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Labonte, F.; Hannington, M. D.; Cousens, B. L.; Blenkinsop, J.; Gill, J. B.; Kelley, D. S.; Lilley, M. D.; Delaney, J. R.

    2006-12-01

    32 sulfide samples from the main structures of the Endeavour vent field, Juan de Fuca Ridge, were analyzed for their Pb isotope composition. The samples were collected from 6 main vent fields between 1985 and 2005 and encompass a strike length of more than 15 km along the ridge crest. The sulfides are typical of black smoker deposits on sediment-starved mid-ocean ridges. Pb isotope compositions of the massive sulfides within the six hydrothermal fields vary within narrow ranges, with 206Pb/204Pb = 18.58 18.75, 207Pb/204Pb = 15.45 15.53 and 208Pb/204Pb = 37.84 38.10. A geographic trend is observed, with the lower Pb ratios restricted mostly to the northern part of the segment (Salty Dawg, Sasquatch and High Rise fields), and the higher Pb ratios restricted mostly to the southern part of the segment (Main Endeavour, Clam Bed and Mothra fields). Variations within individual fields are much smaller than those between fields, and variation within individual sulfide structures is within the uncertainty of the measurements. Therefore, it is unlikely that the ranges of Pb isotope compositions along the length of the segment reflect remobilization, replacement, and recrystallization of sulfides, as suggested for the observed Pb isotope variability in some large seafloor sulfide deposits. Instead, the differences in isotopic compositions from north to south are interpreted to reflect differences in the source rocks exposed to hydrothermal circulation of fluids below the seafloor. Possible sources of the somewhat more radiogenic Pb may be small amounts of buried sediment, either from turbidites or from hemipelagic sediment. This possibility is supported by high concentrations of CH4 and NHC4 found in the high-temperature vent fluids at the Main Endeavour Field, which are interpreted to reflect subseafloor interaction between hydrothermal fluids and organic material in buried sediments. However, the majority of the samples fall below and are approximately parallel to the

  4. Atmospheric control on isotopic composition and d-excess in water vapor over ocean surface

    NASA Astrophysics Data System (ADS)

    Fan, Naixin

    For decades, stable isotopes of water have been used as proxies to infer the variation of the hydrological cycle. However, it is still not clear how various atmospheric processes quantitatively control kinetic fractionation during evaporation over the ocean. Understanding kinetic fractionation is important in that the interpretation of the isotopic composition record preserved in ice cores and precipitation relies in part on the isotopic information at the moisture source. In addition, the isotopic composition of vapor contains information about variation of atmospheric processes such as turbulence and change in moisture source region which is useful for studying meteorological processes and climate change. In this study the isotopic composition of water vapor in the marine boundary layer (MBL) over the ocean was investigated using a combination of a newly developed marine boundary layer (MBL) model and observational data. The new model has a more realistic MBL structure than previous models and includes new features such as vertical advection of air and diffusion coefficients that vary continuously in the vertical direction. A robust linear relationship between deltaD and delta18O was found in observational oceanic water vapor data and the model can well capture the characteristics of this relationship. The individual role of atmospheric processes or variables on deltaD, delta18O and d-excess was quantitatively investigated and an overview of the combined effect of all the meteorological processes is provided. In particular, we emphasize that the properties of subsiding air (such as its mixing ratio and isotopic values) are crucial to the isotopic composition of surface water vapor. Relative humidity has been used to represent the moisture deficit that drives evaporative isotopic fluxes, however, we argue that it has serious limitations in explaining d-excess variation as latitude varies. We introduce a new quantity Gd=SST-Td, the difference between the sea

  5. Re-calculating the pH record from boron isotopic composition of biogenic carbonates

    NASA Astrophysics Data System (ADS)

    Paris, G.; Gaillardet, J.; Louvat, P.

    2010-12-01

    The boron isotopic composition of marine carbonates (δ11Bcarb, ‰) has been proposed as a seawater paleo-acidity proxy (Hemming and Hanson, 1992; Vengosh et al., 1991). This proxy has been extensively used to reconstruct seawater paleo-pH and eventually atmospheric pCO2 during recent times or over short time-scales. However, it requires the knowledge of seawater δ11B value. Boron has a residence time of 10-20 My in seawater, longer than the mixing time of the ocean. The boron isotopic composition of seawater (δ11Bsw) is thus homogeneous in the modern ocean, yet it is not known in the past even though reconstruction and modeling have been attempted that rely on many hypotheses (Lemarchand et al., 2002; Pearson and Palmer, 2000). The boron isotopic composition of Cenozoic evaporites has been recently reconstructed using the direct record of Cenozoic evaporites (Paris et al., 2010). This reconstruction suggests that δ11Bsw has significantly changed along the last 40 Ma, in agreement with other parameters of the oceanic chemical composition. The δ11Bsw change amplitude appears to be stronger than suggested by models. In this presentation, we explore the consequences of this reconstruction on paleo-pH calculation for the late Cenozoic from published boron isotope record in biogenic carbonates (Pearson and Palmer, 2000; Pearson et al., 2009; Seki et al., 2010; Spivack et al., 1993). It points out the inconsistency between different dataset, due to the techniques used for boron isotopic measurement. In conclusion, we suggest that the seawater pH variations are not known with a sufficient precision over the last 35 My and that seawater surface pH could have likely remained constant. Hemming, N.G., and Hanson, G.N. (1992), Boron isotopic composition and concentration in modern marine carbonates: Geochimica et Cosmochimica Acta, v. 56, p. 537-543. Lemarchand, D., et al. (2002), Boron isotope systematics in large rivers: implications for the marine boron budget and

  6. The isotopic composition of silver and lead in two iron meteorites - Cape York and Grant

    NASA Technical Reports Server (NTRS)

    Chen, J. H.; Wasserburg, G. J.

    1983-01-01

    Anomalies in silver isotope composition in the metal phases of the Cape York (IIIA) and Grant (IIIB) iron meteorites are studied together with the lead isotopic composition of both the metal and sulfide phases of Cape York. Following extensive surface cleaning, the Ag-107/Ag-109 ratio in the metal phases of the meteorites is found to be in excess of the terrestrial ratio, and of that found in the sulfide phases. A definite correlation between the Ag-107/Ag-109 and Pd-108/Ag-109 ratios is observed for these meteorites, indicating the in situ decay of Pd-107 and supporting the widespread presence of Pd in the early universe. Lead, determined after cleaning and with chemical separations using low blank levels, is found to exist in variable proportions in the metal and sulfide phases. The sulfides appear to be dominated by radiogenic modern lead, which may be explained by terrestrial contamination or by late metamorphism in the meteorite parent body.

  7. The isotopic composition of silver and lead in two iron meteorites - Cape York and Grant

    NASA Astrophysics Data System (ADS)

    Chen, J. H.; Wasserburg, G. J.

    1983-10-01

    Anomalies in silver isotope composition in the metal phases of the Cape York (IIIA) and Grant (IIIB) iron meteorites are studied together with the lead isotopic composition of both the metal and sulfide phases of Cape York. Following extensive surface cleaning, the Ag-107/Ag-109 ratio in the metal phases of the meteorites is found to be in excess of the terrestrial ratio, and of that found in the sulfide phases. A definite correlation between the Ag-107/Ag-109 and Pd-108/Ag-109 ratios is observed for these meteorites, indicating the in situ decay of Pd-107 and supporting the widespread presence of Pd in the early universe. Lead, determined after cleaning and with chemical separations using low blank levels, is found to exist in variable proportions in the metal and sulfide phases. The sulfides appear to be dominated by radiogenic modern lead, which may be explained by terrestrial contamination or by late metamorphism in the meteorite parent body.

  8. Isotopic compositions and probable origins of organic molecules in the Eocene Messel shale

    NASA Technical Reports Server (NTRS)

    Hayes, J. M.; Takigiku, Ray; Ocampo, Ruben; Callot, Enry J.; Albrecht, Pierre

    1987-01-01

    It is shown here that the carbon isotopic compositions of biomarkers from the Eocene Messel shale, accumulated 47 + or - 2 million years ago in anaerobic waters at the bottom of a lake, allow identification of specific sources for some materials and reconstruction of carbon flows within the lake and its sediments. The C-13 content of organic matter synthesized by lacustrine primary producers can be estimated from the observed C-13 content of the geoporphyrins derived from their chlorophylls. Total organic material in the shale is depleted in C-13 by six parts per thousand relative to that input. This difference cannot be explained by selective loss of components enriched in C-13, nor, as shown by isotopic compositions of other biomarkers, by inputs from land plants surrounding the lake or from methanogenic bacteria.

  9. Os isotopic composition of steels: Constraints on sources of Os in steel & crustal isotopic evolution of iron ores

    NASA Astrophysics Data System (ADS)

    Chatterjee, R. N.; Lassiter, J. C.

    2013-12-01

    Metal contamination during sample processing is a potential concern in Os-isotope studies. We examined Os concentrations and Os isotopes in industrial steels. Samples include high Cr stainless steels (>10.5% Cr), low alloy steels (>=92% Fe) and high alloy steels (<92% Fe). The chief components used to make steel are iron ore, chromites and coke. Coke is derived from coals that have low Os concentration (~36 ppt) [1]. Chromites in steels are mined from chromitites, which have high average Os concentrations and mantle-like 187Os/188Os ratios (~88 ppb Os, 187Os/188Os ≈ 0.127×24) [2]. Iron ores used in US steel manufacturing derive chiefly from magnetites mined from iron-bearing formations such as Banded Iron Formations (BIF), which have median Os concentration of ~4.8 ppb and radiogenic 187Os/188Os ≈ 0.358×388 [3]. Os concentrations in the measured steels span a wide range, from 0.03 to 22 ppb. The 187Os/188Os ratios vary from 0.144-4.12. Such high Os concentrations and radiogenic isotopic compositions confirm that metal contamination can affect Os-isotope compositions during sample processing, particularly for low-[Os] samples. There is no correlation between C and Os concentration in steel, indicating that coke is not a major Os source in steels. Os concentrations in steels are positively correlated with Cr content, suggesting that chromite-derived Os dominates the Os budget in stainless steels. 187Os/188Os is negatively correlated with Cr content, ranging from 0.144-0.195 in high-Cr (>10.5 % Cr) steels but from 0.279-4.12 in low-Cr steels. In addition, there is a positive correlation between 1/Os and 187Os/188Os, consistent with two-component mixing of Os derived from magnetite ore and chromites. Lower Os concentrations in steels than expected from simple mixing of magnetite and chromitite suggest some volatile Os loss during smelting. Although the current data is limited, the 186Os-187Os trend defined by the steel analyses can be utilized to extrapolate

  10. In-Situ Oxygen Isotopic Composition of Tagish Lake: An Ungrouped Type 2 Carbonaceous Chondrite

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael E.; Engrand, Cecile; Gounelle, Matthieu; Zolensky, Mike E.

    2001-01-01

    We have measured the oxygen isotopic composition of several components of Tagish Lake by ion microprobe. This meteorite constitutes the best preserved sample of C2 matter presently available for study. It presents two different lithologies (carbonate-poor and -rich) which have fairly comparable oxygen isotopic composition, with regard to both the primary or secondary minerals. For the olivine and pyroxene grains, their delta O-18 values range from - 10.5% to + 7.4% in the carbonate-poor lithology, with a mean Delta O-17 value of - 3.7 2.4%. In the carbonate-rich lithology, delta O-18 varies from - 7.9% to + 3.3%, and the mean Delta O-17 value is - 4.7 +/- 1.4%. Olivine inclusions (Fo(sub >99)) with extreme O-16-enrichment were found in both lithologies: delta O-18 = - 46.1 %, delta O-187= - 48.3% and delta O-18 = - 40.6%, delta O-17 = - 41.2% in the carbonate-rich lithology; delta O-18 = - 41.5%, delta O-17 = -43.4%0 in the carbonate-poor lithology. Anhydrous minerals in the carbonate-poor lithology are slightly more O-16-rich than in the carbonate-rich one. Four low-iron manganese-rich (LIME) olivine grains do not have an oxygen isotopic composition distinct from the other "normal" olivines. The phyllosilicate matrix presents the same range of oxygen isotopic compositions in both lithologies: delta O-18 from approximately 11 % to approximately 6%, with an average Delta. O-17 approximately 0%. Because the bulk Tagish Lake oxygen isotopic composition given by Brown et al. is on the high end of our matrix analyses, we assume that this "bulk Tagish Lake" composition probably only represents that of the carbonate-rich lithology. Calcium carbonates have delta O-18 values up to 35%, with Delta O-17 approximately 0.5%0. Magnetite grains present very high Delta O-17 values approximately + 3.4%0 +/- 1.2%. Given our analytical uncertainties and our limited carbonate data, the matrix and the carbonate seem to have formed in isotopic equilibrium. In that case, their large

  11. Isotopic Composition of Natural Nitrate in Groundwater in Los Alamos, New Mexico, USA

    NASA Astrophysics Data System (ADS)

    Chrystal, A. E.; Heikoop, J. M.; Longmire, P.; Dale, M.; Larson, T. E.; Perkins, G.; Fabyrka-Martin, J.; Simmons, A. M.; Fessenden-Rahn, J.

    2009-12-01

    Los Alamos National Laboratory (LANL) has established background concentrations for various dissolved constituents in local groundwater from perched-intermediate and regional aquifers in the vicinity of Los Alamos in north-central New Mexico. Typical background concentrations of nitrate (NO3-) are on the order of 0.31 mg/L as N (0.02 mM/L). In addition to natural sources, anthropogenic sources of NO3- in local groundwaters include industrial and treated sewage discharges released from LANL facilities, and treated sewage effluent discharges from Los Alamos County. We are using stable isotopes of nitrogen and oxygen in NO3- to distinguish among these sources, define groundwater flow paths, and evaluate groundwater mixing. Following the approach of McMahon and Böhlke (2006), we have explored the δ18O[NO3-] of water samples taken from background wells and springs in the Los Alamos area. NO3- from a spring and a well located in the Valles caldera, upgradient and upwind (relative to prevailing winds) of Los Alamos has δ15N and δ18O values of approximately 4.8 ‰ and -2.6 ‰, respectively. Tritium and unadjusted radiocarbon analyses indicate that these caldera waters predate LANL operations commencing in 1943. NO3- from groundwater locations in Los Alamos that exhibit background conditions has isotopic values similar to those of the caldera groundwater. Because local groundwater is relatively oxidizing, denitrification is not expected to be a factor in altering isotopic compositions of NO3-. Results indicate that there is little direct atmospheric contribution to dissolved NO3-, and that most NO3- is derived from bacterial nitrification in which one oxygen atom comes from atmospheric oxygen and two oxygen atoms come from soil porewater. Oxygen isotope values plot slightly below the expected isotopic trend for a 1:2 mix of these two sources, indicating either slight fractionation of oxygen isotopes during nitrification, or potential mixing with geological sources of

  12. Assessment of the clumped isotope composition of fossil bone carbonate as a recorder of subsurface temperatures

    NASA Astrophysics Data System (ADS)

    Suarez, Marina B.; Passey, Benjamin H.

    2014-09-01

    Bone is susceptible to early diagenesis, and its carbon and oxygen isotopic compositions have been suggested to reflect conditions in the soil environment and shallow subsurface during fossilization. This implies open-system recrystallization involving mass exchange of carbon and oxygen among bioapatite, soil water, and DIC. Such recrystallization would also redistribute isotopic clumping (including 13C-18O bonds), leading to the possibility that the carbonate clumped isotope compositions of fossil bone record ground temperature during early diagenesis. We assess this possibility by studying Quaternary mammalian fossil bone from subtropical to polar latitudes: if recrystallization is early and pervasive, clumped isotope derived temperatures, T(Δ47), should closely mirror latitudinal gradients in ground temperature. Excluding results from a mummified specimen yielding T(Δ47) = 38 °C (that is, indistinguishable from mammalian body temperature), we find that T(Δ47) values are intermediate between mammalian body temperature and ground temperature, suggesting partial recrystallization of bone carbonate. XRD analyses show that the nature and extent of diagenesis varies among the samples and does not relate in a straightforward manner to T(Δ47). No clear correlation exists between T(Δ47) and mean annual temperature or mean warm season temperature. Furthermore, bone tends to retain the 18O-enriched signature of body water, suggesting incomplete oxygen isotope exchange with meteoric waters. Incomplete carbon and oxygen isotope exchange between bone carbonate and soil waters is also indicated for a set of late Miocene bone-enamel pairs from a sequence of stacked paleosols in northern China. Analysis of bone as old as Early Cretaceous shows that bone carbonate is susceptible to later diagenesis at elevated burial temperatures, although T(Δ47) does not closely conform to maximum burial temperature, again suggesting partial recrystallization, or recrystallization during

  13. Where Did the Ureilite Parent Body Accrete? Constraints from Chemical and Isotopic Compositions

    NASA Astrophysics Data System (ADS)

    Goodrich, Cyrena; O'Brien, David P.

    2014-11-01

    Almahata Sitta and other polymict ureilites contain a remarkable diversity of materials, including EH, EL, OC, R- and CB chondrites, in addition to the dominant ureilitic material [1]. These materials represent at least 6 different parent asteroids and a wide range of chemical and isotopic environments in the early Solar System. To understand the origin of this diversity it is critical to know where (heliocentric distance) the ureilite parent body (UPB) accreted. The chemical and isotopic compositions of ureilite precursors (inferred from the compositions of ureilites) can provide clues. Lithophile element ratios such as Si/Mg and Mn/Mg [2,3], and deficits in neutron-rich Cr, Ti and Ni isotopes [3], indicate that ureilite precursors were similar to ordinary or enstatite chondrites (OC or EC), not carbonaceous chondrites (CC). In contrast, high carbon contents, carbon isotopes and oxygen isotopes suggest a genetic link to CC. This poses a conundrum considering the variation of asteroid types, which suggests that EC and OC dominate the inner asteroid belt and CC the outer belt. However, the CC-like oxygen isotopes of ureilites strongly suggest the effects of parent-body aqueous alteration [4,5], which clearly implies that the UPB accreted beyond the ice line. Lithophile element properties of ureilites compared with chondrites may not be a reliable indicator of location of accretion, because lithophile elements in chondrites are sited mainly in chondrules and the UPB accreted before most chondrules formed [6]. Ureilite Cr, Ti and Ni isotopes may indicate late introduction of the neutron rich isotopes of these elements to the CC-formation region [7]. We conclude that the UPB accreted in the outer belt, like CC. The UPB or one of its offspring must have migrated to the inner belt to acquire OC, EC and R-chondrite materials.[1] Horstmann M. & Bischoff A. [2014] Chemie der Erde 74, 149.[2] Goodrich C. [1999] MAPS 34, 109.[3] Warren P. [2011] GCA 46, 53.[4] Young E. [1999

  14. Carbon isotope composition of carbonaceous matter from the precambrian of the witwatersrand system.

    PubMed

    Hoefs, J; Schidlowski, M

    1967-03-03

    Polymerized hydrocarbons occurring in the gold-uranium conglomerates of the Witwatersrand System (South Africa) show deltaC(13) values between -22.4 and -32.8 per mille, their isotopic composition thus falling into the range of sedimentary organic carbon. Accordingly, organic derivation of the material seems very probable. This conclusion is consistent with a model of the existence of organic evolution and biologic activity in times certainly older than 2.15 x 10(9) years.

  15. Mineralogy and Oxygen Isotope Compositions of an Unusual Hibonite-Perovskite Refractory Inclusion from Allende

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Snead, C.; Rahman, Z.; McKeegan, K. D.

    2012-01-01

    Hibonite-rich Ca- and Al-rich inclusions (CAIs) are among the earliest formed solids that condensed in the early nebula. We discovered an unusual refractory inclusion from the Allende CV3 chondrite (SHAL) containing an approx 500 micron long single crystal of hibonite and co-existing coarse-grained perovskite. The mineralogy and petrography of SHAL show strong similarities to some FUN inclusions, especially HAL. Here we report on the mineralogy, petrography, mineral chemistry and oxygen isotopic compositions in SHAL.

  16. Microscale determination of the spectral characteristics and carbon-isotopic compositions of porphyrins

    NASA Technical Reports Server (NTRS)

    Popp, B. N.; Hayes, J. M.; Boreham, C. J.

    1993-01-01

    Molar extinction coefficients for band III of Ni porphyrins are calculated from results of spectrophotometric and manometric analyses of individual etioporphyrins, DPEP, cyclic, and diDPEP porphyrins known to initially be pure from mass spectrometry, 1H NMR, and analytical HPLC studies. A method for determining carbon-isotopic compositions and purity of micromolar quantities of individual porphyrins using combined spectrophotometric and manometric techniques is presented.

  17. Spatial variability in the isotopic composition of rainfall in a small headwater catchment and its effect on hydrograph separation

    NASA Astrophysics Data System (ADS)

    Fischer, Benjamin M. C.; van Meerveld, H. J. (Ilja); Seibert, Jan

    2017-04-01

    Isotope hydrograph separation (IHS) is a valuable tool to study runoff generation processes. To perform an IHS, samples of baseflow (pre-event water) and streamflow are taken at the catchment outlet. For rainfall (event water) either a bulk sample is collected or it is sampled sequentially during the event. For small headwater catchment studies, event water samples are usually taken at only one sampling location in or near the catchment because the spatial variability in the isotopic composition of rainfall is assumed to be small. However, few studies have tested this assumption. In this study, we investigated the spatiotemporal variability in the isotopic composition of rainfall and its effects on IHS results using detailed measurements from a small pre-alpine headwater catchment in Switzerland. Rainfall was sampled sequentially at eight locations across the 4.3 km2 Zwäckentobel catchment and stream water was collected in three subcatchments (0.15, 0.23, and 0.70 km2) during ten events. The spatial variability in rainfall amount, average and maximum rainfall intensity and the isotopic composition of rainfall was different for each event. There was no significant relation between the isotopic composition of rainfall and total rainfall amount, rainfall intensity or elevation. For eight of the ten studied events the temporal variability in the isotopic composition of rainfall was larger than the spatial variability in the rainfall isotopic composition. The isotope hydrograph separation results, using only one rain sampler, varied considerably depending on which rain sampler was used to represent the isotopic composition of event water. The calculated minimum pre-event water contributions differed up to 60%. The differences were particularly large for events with a large spatial variability in the isotopic composition of rainfall and a small difference between the event and pre-event water isotopic composition. Our results demonstrate that even in small catchments

  18. Investigating the source, transport, and isotope composition of water vapor in the planetary boundary layer

    NASA Astrophysics Data System (ADS)

    Griffis, Timothy J.; Wood, Jeffrey D.; Baker, John M.; Lee, Xuhui; Xiao, Ke; Chen, Zichong; Welp, Lisa R.; Schultz, Natalie M.; Gorski, Galen; Chen, Ming; Nieber, John

    2016-04-01

    Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle - an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understand feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor at a very tall tower (185 m) in the upper Midwest, United States, to diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotope observations for this region. Several simple isotope models and cross-wavelet analyses were used to assess the importance of the Rayleigh distillation process, evaporation, and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a large seasonal amplitude (mean monthly δ18Ov ranged from -40.2 to -15.9 ‰ and δ2Hv ranged from -278.7 to -113.0 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio when considering the entire hourly data set. However, this relation was strongly modulated by evaporation and PBL entrainment processes at timescales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess (dv) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that evaporation often leads changes in dv, confirming that it is a potential tracer of regional evaporation. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional evaporation. However, isoforcing calculations and mixing model analyses for high PBL water vapor mixing ratio events ( > 25 mmol mol-1) indicate that regional evaporation can account

  19. Investigating the source, transport, and isotope composition of water vapor in the planetary boundary layer

    SciTech Connect

    Griffis, Timothy J.; Wood, Jeffrey D.; Baker, John M.; Lee, Xuhui; Xiao, Ke; Chen, Zichong; Welp, Lisa R.; Schultz, Natalie M.; Gorski, Galen; Chen, Ming; Nieber, John

    2016-04-25

    Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle – an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understand feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor at a very tall tower (185 m) in the upper Midwest, United States, to diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotope observations for this region. Several simple isotope models and cross-wavelet analyses were used to assess the importance of the Rayleigh distillation process, evaporation, and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a large seasonal amplitude (mean monthly δ18Ov ranged from –40.2 to –15.9 ‰ and δ2Hv ranged from –278.7 to –113.0 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio when considering the entire hourly data set. However, this relation was strongly modulated by evaporation and PBL entrainment processes at timescales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess (dv) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that evaporation often leads changes in dv, confirming that it is a potential tracer of regional evaporation. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional evaporation. However, isoforcing calculations and mixing model analyses for

  20. Li Isotopic Composition and Concentration of the Upper Continental Crust: New Insights from Desert Loess

    NASA Astrophysics Data System (ADS)

    Sauzeat, L.; Rudnick, R. L.; Chauvel, C.

    2014-12-01

    The isotopic composition of lithium (δ7Li) is recognized to be an excellent proxy of near-surface fluid-rock reactions during weathering. Using Li as a tracer of these processes however requires constraints on the average Li composition of terrestrial reservoirs, in particular that of the upper continental crust. To date, only one value for the average δ7Li value of the upper continental crust, derived from periglacial loess, shales, and granites is available in the literature (7δLi = 0 ± 4 (2σ), Teng et al., 2004). Several values exist for the average [Li] of the upper crust, but they differ by more than 30%. We measured the Li isotopic composition of about 30 desert and periglacial loess (unweathered windblown sediments) from several parts of the world (Europe, Argentina, China and Tajikistan). We demonstrate that desert loess, which is more homogeneous and representative of larger portions of the Earth's surface, provides a better proxy for the average composition of the upper continental crust compared to periglacial loess. The Li isotopic compositions and concentrations of desert loess are controlled by eolian sorting, which can be quantified as a binary isotopic mixing between a weathered fine-grained end-member and an unweathered coarse-grained end-member. Using correlations between Li isotopic compositions, Li concentrations and trace element concentrations in desert loess, we estimate new average values for the upper continental crust: 1 ± 2 (2σ); [Li] = 35.3 ± 4.6 (2σ) ppm. This δ7Li value is slightly higher than that previously published in Teng et al. (2004), but overlaps within uncertainty, whereas the [Li] is identical to that of Teng et al. (2004: 35 ± 11, 2σ); both new estimates have lower uncertainty. Our new estimate of [Li], along with that of Teng et al. (2004), are higher than all previous estimates for the upper continental crust, raising the question as to whether the average concentrations of other mobile alkali metals such as

  1. Boron isotopic composition of tourmaline from massive sulfide deposits and tourmalinites

    USGS Publications Warehouse

    Palmer, M.R.; Slack, J.F.

    1989-01-01

    Boron isotope ratios (11B/10B) have been measured on 60 tourmaline separates from over 40 massive sulfide deposits and tourmalinites from a variety of geologic and tectonic settings. The coverage of these localities is global (5 continents) and includes the giant ore bodies at Kidd Creek and Sullivan (Canada), Broken Hill (Australia), and Ducktown (USA). Overall, the tourmalines display a wide range in ??11B values from -22.8 to +18.3??? Possible controls over the boron isotopic composition of the tourmalines include: 1) composition of the boron source, 2) regional metamorphism, 3) water/rock ratios, 4) seawater entrainment, 5) temperature of formation, and 6) secular variations in seawater ??11B. The most significant control appears to be the composition of the boron source, particularly the nature of footwall lithologies; variations in water/ rock ratios and seawater entrainment are of secondary importance. The boron isotope values seem especially sensitive to the presence of evaporites (marine and non-marine) and carbonates in source rocks to the massive sulfide deposits and tourmalinites. ?? 1989 Springer-Verlag.

  2. Absolute Zero

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell J.; Sheibley, D.; Belloni, M.; Stamper-Kurn, D.; Vinen, W. F.

    2006-12-01

    Absolute Zero is a two hour PBS special attempting to bring to the general public some of the advances made in 400 years of thermodynamics. It is based on the book “Absolute Zero and the Conquest of Cold” by Tom Shachtman. Absolute Zero will call long-overdue attention to the remarkable strides that have been made in low-temperature physics, a field that has produced 27 Nobel Prizes. It will explore the ongoing interplay between science and technology through historical examples including refrigerators, ice machines, frozen foods, liquid oxygen and nitrogen as well as much colder fluids such as liquid hydrogen and liquid helium. A website has been established to promote the series: www.absolutezerocampaign.org. It contains information on the series, aimed primarily at students at the middle school level. There is a wealth of material here and we hope interested teachers will draw their student’s attention to this website and its substantial contents, which have been carefully vetted for accuracy.

  3. Solar Wind Fractionation — Isotopic and Elemental — and Implications for Solar Compositions and Future Genesis Analyses

    NASA Astrophysics Data System (ADS)

    Wiens, R. C.; Reisenfeld, D. B.; Heber, V. S.; Burnett, D. S.

    2010-03-01

    Fractionation between solar wind and the solar photosphere is substantial, both for elements and isotopes. GENESIS measurements are key to understanding these fractionations, which will in turn provide more accurate solar compositions.

  4. Variations in the O-isotope composition of gas during the formation of chondrules from the CR chondrites

    NASA Astrophysics Data System (ADS)

    Schrader, Devin L.; Nagashima, Kazuhide; Krot, Alexander N.; Ogliore, Ryan C.; Hellebrand, Eric

    2014-05-01

    To better understand the environment of chondrule formation and constrain the O-isotope composition of the ambient gas in the Renazzo-like carbonaceous (CR) chondrite chondrule-forming region, we studied the mineralogy, petrology, and in situ O-isotope compositions of olivine in 11 barred olivine (BO) chondrules and pyroxene and silica in three type I porphyritic chondrules from the CR chondrites Gao-Guenie (b), Graves Nunataks (GRA) 95229, Pecora Escarpment (PCA) 91082, and Shişr 033. BO chondrules experienced a higher degree of melting than porphyritic chondrules, and therefore, it has been hypothesized that they more accurately recorded the O-isotope composition of the gas in chondrule-forming regions. We studied the O-isotope composition of silica as it has been hypothesized to have formed via direct condensation from the gas.

  5. Composition of Hydrothermal Vent Microbial Communities as Revealed by Analyses of Signature Lipids, Stable Carbon Isotopes and Aquificales Cultures

    NASA Technical Reports Server (NTRS)

    Jahnke, L. L.; Eder, W.; Huber, Robert; Hinrichs, K-U.; Hayes, J. M.; DesMarais, D. J.; Cady, S. L.; Hope, J. M.; Summons, R. E.

    2001-01-01

    This paper describes a study of lipid biomarker composition and carbon isotopic fractionation in cultured Aquificales and natural analogues from Yellowstone National Park. Additional information is contained in the original extended abstract.

  6. The Triple Oxygen Isotopic Composition of High 3He/4He Mantle

    NASA Astrophysics Data System (ADS)

    Jackson, C.; Parman, S. W.; Starkey, N.; Greenwood, R.; Franchi, I.; Jackson, M. G.; Fitton, J. G.; Stewart, F. M.; Larsen, L. M.

    2015-12-01

    Measurements of Xe isotope ratios in ocean island basalts (OIB) suggest that Earth's mantle accreted heterogeneously, and that compositional remnants of accretion are sampled by modern, high-3He/4He OIB associated with the Icelandic and Samoan plumes [1]. If so, the high-3He/4He source may also have a distinct oxygen isotopic composition from the rest of the mantle. Here, we test if the major elements of the high-3He/4He source preserve any evidence of heterogeneous accretion using measurements of three oxygen isotopes on olivine from a variety of high-3He/4He OIB locations. To high precision, the ∆17O value of high-3He/4He olivines from Hawaii, Pitcairn, Baffin Island and Samoa, are indistinguishable from bulk mantle olivine (Δ17OBulk Mantle - Δ17OHigh 3He/4He olivine = -0.002 ± 0.004 (2 x SEM) ‰). Thus, there is no resolvable oxygen isotope evidence for heterogeneous accretion in the high-3He/4He source. Modelling of mixing processes indicates that if an early-forming, oxygen-isotope distinct mantle did exist, either the anomaly was extremely small, or the anomaly was homogenised away by later mantle convection. The δ18O values of olivine with the highest 3He/4He ratios from a variety of OIB locations have a relatively uniform composition (~5 ‰). This composition is intermediate to values associated with the depleted MORB mantle and the average mantle. Similarly, δ18O values of olivine from high-3He/4He OIB correlate with radiogenic isotope ratios of He, Sr, and Nd. Combined, this suggests that oxygen remains coupled to the more incompatible elements during melt production and migration and that the intermediate δ18O value is a feature of the mantle source. The processes responsible for the δ18O signature of high-3He/4He mantle are not certain, but δ18O-87Sr/86Sr correlations indicate that it may be connected to a predominance of a HIMU-like (high U/Pb) component or other moderate δ18O components recycled into the high-3He/4He source. [1] S

  7. Triple oxygen isotopic composition of the high-3He/4He mantle

    NASA Astrophysics Data System (ADS)

    Starkey, N. A.; Jackson, C. R. M.; Greenwood, R. C.; Parman, S.; Franchi, I. A.; Jackson, M.; Fitton, J. G.; Stuart, F. M.; Kurz, M.; Larsen, L. M.

    2016-03-01

    Measurements of Xe isotope ratios in ocean island basalts (OIB) suggest that Earth's mantle accreted heterogeneously, and that compositional remnants of accretion are sampled by modern, high-3He/4He OIB associated with the Icelandic and Samoan plumes. If so, the high-3He/4He source may also have a distinct oxygen isotopic composition from the rest of the mantle. Here, we test if the major elements of the high-3He/4He source preserve any evidence of heterogeneous accretion using measurements of three oxygen isotopes on olivine from a variety of high-3He/4He OIB locations. To high precision, the Δ17O value of high-3He/4He olivines from Hawaii, Pitcairn, Baffin Island and Samoa, are indistinguishable from bulk mantle olivine (Δ17OBulk Mantle - Δ17OHigh 3He/4He olivine = -0.002 ± 0.004 (2 × SEM)‰). Thus, there is no resolvable oxygen isotope evidence for heterogeneous accretion in the high-3He/4He source. Modelling of mixing processes indicates that if an early-forming, oxygen-isotope distinct mantle did exist, either the anomaly was extremely small, or the anomaly was homogenised away by later mantle convection. The δ18O values of olivine with the highest 3He/4He ratios from a variety of OIB locations have a relatively uniform composition (∼5‰). This composition is intermediate to values associated with the depleted MORB mantle and the average mantle. Similarly, δ18O values of olivine from high-3He/4He OIB correlate with radiogenic isotope ratios of He, Sr, and Nd. Combined, this suggests that magmatic oxygen is sourced from the same mantle as other, more incompatible elements and that the intermediate δ18O value is a feature of the high-3He/4He mantle source. The processes responsible for the δ18O signature of high-3He/4He mantle are not certain, but δ18O-87Sr/86Sr correlations indicate that it may be connected to a predominance of a HIMU-like (high U/Pb) component or other moderate δ18O components recycled into the high-3He/4He source.

  8. Tracking nitrous oxide emission processes at a suburban site with semicontinuous, in situ measurements of isotopic composition

    NASA Astrophysics Data System (ADS)

    Harris, Eliza; Henne, Stephan; Hüglin, Christoph; Zellweger, Christoph; Tuzson, Béla; Ibraim, Erkan; Emmenegger, Lukas; Mohn, Joachim

    2017-02-01

    The isotopic composition of atmospheric nitrous oxide (N2O) was measured semicontinuously, at ˜35 min frequency in intermittent periods of 1-6 days over one and a half years, using preconcentration coupled to a quantum cascade laser spectrometer at the suburban site of Dübendorf, Switzerland. The achieved measurement repeatability was 0.08‰, 0.11‰, and 0.10‰ for δ18O, site preference, and δ15Nbulk respectively, which is better than or equal to standard flask sampling-based isotope ratio mass spectrometry performance. The observed mean diurnal cycle reflected the buildup of N2O from isotopically light sources on an isotopically heavy tropospheric background. The measurements were used to determine the source isotopic composition, which varied significantly compared to chemical and meteorological parameters monitored at the site. FLEXPART-COSMO transport modeling in combination with modified Emissions Database for Global Atmospheric Research inventory emissions was used to model N2O mole fractions at the site. Additionally, isotopic signatures were estimated for different source categories using literature data and used to simulate N2O isotopic composition over the measurement period. The model was able to capture variability in N2O mole fraction well, but simulations of isotopic composition showed little agreement with observations. In particular, measured source isotopic composition exhibited one magnitude larger variability than simulated, clearly indicating that the range of isotopic source signatures estimated from literature significantly underestimates true variability of source signatures. Source δ18O signature was found to be the most sensitive tracer for urban/industry versus agricultural N2O. δ15Nbulk and site preference may provide more insight into microbial and chemical emission processes than partitioning of anthropogenic source categories.

  9. The triple oxygen isotope composition of leaf waters in Mpala, central Kenya

    NASA Astrophysics Data System (ADS)

    Li, S.; Levin, N.; Soderberg, K.; Dennis, K. J.; Caylor, K. K.

    2013-12-01

    The triple oxygen isotopic composition of water is an emerging tool for investigating the hydrological environment. The δ18O-δ17O relationship differs during kinetic and equilibrium isotope fractionation, such that the 17O depletion can be sensitive to relative humidity (Rh) during kinetic fractionation, mixing among different pools, and to the specific mode of kinetic fractionation. It has been proposed that the δ18O-δ17O relationship during evapotranspiration, as characterized by the slope λ(stem-leaf) on a ln(δ17O+1) vs. ln(δ18O+1) plot, is mainly controlled by Rh but not affected by other environmental conditions or by plant species. In order to understand the sensitivity of λ(stem-leaf) to Rh and the utility of 17O-excess (the deviation of δ17O from a reference slope) in the terrestrial biosphere as a tracer of Rh conditions today and in the past, this study expands the triple oxygen isotope measurements of leaf waters to additional species in a semiarid environment. Paired stem and leaf waters of Acacia and grasses were collected in the Mpala Research Center in central Kenya and analyzed for their triple oxygen isotope composition. Leaf waters that were sampled diurnally (8 sampling intervals between 6 am and 5 pm) exhibit a range in δ18O and 17O-excess values of 11.2‰ and 107 per meg respectively for Acacia brevispica, and 14.4‰ and 147 per meg for the grass Panicum maximum. Except for one sample collected at 7am, the λ(stem-leaf) values for grasses are systematically lower (0.0012 to 0.0110) than Acacia λ(stem-leaf) values at the corresponding time of day; this might be explained by the progressive evaporative isotopic enrichment and mixing processes of leaf water along parallel veins of grass leaves. Most of the triple oxygen isotope composition of the Acacia leaf waters can be predicted using Craig-Gordon model. We built a mass balance model of an evolving leaf water system from nonsteady-state to steady-state conditions during

  10. The oxygen isotope composition of nitrate generated by nitrification in acid forest floors

    NASA Astrophysics Data System (ADS)

    Mayer, Bernhard; Bollwerk, Sandra M.; Mansfeldt, Tim; Hütter, Birgit; Veizer, Jan

    2001-09-01

    The oxygen isotope composition of nitrate is used increasingly for identifying the origin of nitrate in terrestrial and aquatic ecosystems. This novel isotope tracer technique is based on the fact that nitrate in atmospheric deposition, in fertilizers, and nitrate generated by nitrification in soils appear to have distinct oxygen isotope ratios. While the typical ranges of δ 18O values of nitrate in atmospheric deposition and fertilizers are comparatively well known, few experimental data exist for the oxygen isotope composition of nitrate generated by nitrification in soils. The objective of this study was to determine δ 18O values of nitrate formed by microbial nitrification in acid forest floors. Evidence from laboratory incubation experiments and field studies suggests that during microbial nitrification in acid forest floor horizons, up to two of the three oxygen atoms in newly formed nitrate are derived from water, particularly if ammonium is abundant and nitrification rates are high. It was, however, also observed that in ammonium-limited systems with low nitrification rates, significantly less than two thirds of the oxygen in newly formed nitrate can be derived from water oxygen, presumably as a result of heterotrophic nitrification. It can be concluded from the presented data that the δ 18O values of nitrate formed by microbial nitrification in acid forest floors typically range between +2 and +14‰, assuming that soil water δ 18O values vary between -15 and -5‰. Hence, oxygen isotope ratios of nitrate formed by nitrification in forest floors are usually distinct from those of other nitrate sources such as atmospheric deposition and synthetic fertilizers and, therefore, constitute a valuable qualitative tracer for distinguishing among these sources of nitrate. A quantitative source apportionment appears, however, difficult because of the wide range of δ 18O values, particularly for atmospheric nitrate deposition and for nitrate from microbial

  11. The isotopic composition of uranium and lead in Allende inclusions and meteoritic phosphates

    NASA Technical Reports Server (NTRS)

    Chen, J. H.; Wasserburg, G. J.

    1981-01-01

    The isotopic compositions of uranium and lead in Ca-Al-rich inclusions from the Allende chondrite and in whitlockite from the St. Severin chondrite and the Angra dos Reis achondrite are reported. Isoptopic analysis of acid soluble fractions of the Allende inclusions and the meteoritic whitlockite, which show isotopic anomalies in other elements, reveals U-235/U-238 ratios from 1/137.6 to 1/138.3, within 20 per mil of normal terrestrial U abundances. The Pb isotopic compositions of five coarse-grained Allende inclusions give a mean Pb-207/Pb-206 model age of 4.559 + or - 0.015 AE, in agreement with the U results. Pb isotope ratios of two fine-grained inclusions and a coarse-grained inclusion with strong mass fractionation and some nonlinear isotopic anomalies indicate that the U-Pb systems of these inclusions have evolved differently from the rest of Allende. Th/U abundance ratios in the Allende inclusions and meteoritic phosphate are found to range from 3.8 to 96, presumably indicating an optimal case for Cm/U fractionation, although the normal U concentrations do not support claims of abundant live Cm-247 or Cm-247/U-238 fractionation at the time of meteorite formation, in contrast to previous results. A limiting Cm-247/U-235 ratio of 0.004 at the time of meteorite formation is calculated which implies that the last major r process contribution at the protosolar nebula was approximately 100 million years prior to Al-26 formation and injection.

  12. Isotopic Composition of Cadmium across the Subtropical Convergence in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Gault-Ringold, M.; Stirling, C. H.; Frew, R.; Hunter, K. A.

    2010-12-01

    The almost linear relationship between cadmium (Cd) and phosphate (PO4) in the oceans has been used extensively as a paleoproxy to investigate historical nutrient cycling (Boyle, 1992, Annu. Rev. Earth Planet. Sci. 20, 245). However, our limited understanding of oceanic Cd cycling and the mechanism of the Cd/PO4 relationship limits the reliability of this paleoproxy (Elderfield and Rickaby, 2000, Nature. 405, 305), particularly in the surface waters of the Southern Ocean. Recent studies have shown that the biological uptake of Cd by phytoplankton can create significant (permil-level) isotopic shifts between the phytoplankton and surface ocean water (Ripperger and Rehkamper, 2007, Earth Planet. Sci. Lett. 261, 670) suggesting that Cd isotopes have the potential to provide more information about the marine cycling of Cd than concentration measurements alone. The subtropical convergence (STC) in the Southern Ocean has some of the world’s lowest Cd:PO4 ratios (Frew and Hunter, 1995, Mar. Chem. 51, 223) and provides an ideal location to study the biogeochemical cycling of Cd in the marine environment. Utilizing double-spiking protocols combined with multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS) (Ripperger and Rehkamper, 2007, Geochim. Cosmochim. Acta. 71, 631), we have determined the isotopic composition of Cd in seawater samples collected from the Otago transect off the southeast coast of New Zealand. This transect intersects the STC, passing through both subtropical (iron replete) and subantarctic (HNLC) water masses. Samples were collected seasonally from May 2008 through January 2010 to identify seasonal variability of isotopic composition and concentration due to changes in water mass chemistry and biological activity. This Cd isotope data will help determine the mechanisms controlling Cd uptake in the Southern Ocean and provide insight into the effectiveness of the current Cd/PO4 paleoproxy helping to improve its application.

  13. Isotopic composition for source identification of mercury in atmospheric fine particles

    NASA Astrophysics Data System (ADS)

    Huang, Qiang; Chen, Jiubin; Huang, Weilin; Fu, Pingqing; Guinot, Benjamin; Feng, Xinbin; Shang, Lihai; Wang, Zhuhong; Wang, Zhongwei; Yuan, Shengliu; Cai, Hongming; Wei, Lianfang; Yu, Ben

    2016-09-01

    The usefulness of mercury (Hg) isotopes for tracing the sources and pathways of Hg (and its vectors) in atmospheric fine particles (PM2.5) is uncertain. Here, we measured Hg isotopic compositions in 30 potential source materials and 23 PM2.5 samples collected in four seasons from the megacity Beijing (China) and combined the seasonal variation in both mass-dependent fractionation (represented by the ratio 202Hg / 198Hg, δ202Hg) and mass-independent fractionation of isotopes with odd and even mass numbers (represented by Δ199Hg and Δ200Hg, respectively) with geochemical parameters and meteorological data to identify the sources of PM2.5-Hg and possible atmospheric particulate Hg transformation. All PM2.5 samples were highly enriched in Hg and other heavy metals and displayed wide ranges of both δ202Hg (-2.18 to 0.51 ‰) and Δ199Hg (-0.53 to 0.57 ‰), as well as small positive Δ200Hg (0.02 to 0.17 ‰). The results indicated that the seasonal variation in Hg isotopic composition (and elemental concentrations) was likely derived from variable contributions from anthropogenic sources, with continuous input due to industrial activities (e.g., smelting, cement production and coal combustion) in all seasons, whereas coal combustion dominated in winter and biomass burning mainly found in autumn. The more positive Δ199Hg of PM2.5-Hg in spring and early summer was likely derived from long-range-transported Hg that had undergone extensive photochemical reduction. The study demonstrated that Hg isotopes may be potentially used for tracing the sources of particulate Hg and its vectors in the atmosphere.

  14. Chemistry and oxygen isotopic composition of cluster chondrite clasts and their components in LL3 chondrites

    NASA Astrophysics Data System (ADS)

    Metzler, Knut; Pack, Andreas

    2016-02-01

    Cluster chondrites are characterized by close-fit textures of deformed and indented chondrules, taken as evidence for hot chondrule accretion (Metzler). We investigated seven cluster chondrite clasts from six brecciated LL3 chondrites and measured their bulk oxygen isotopic and chemical composition, including REE, Zr, and Hf. The same parameters were measured in situ on 93 chondrules and 4 interchondrule matrix areas. The CI-normalized REE patterns of the clasts are flat, showing LL-chondritic concentrations. The mean chemical compositions of chondrules in clasts and other LL chondrites are indistinguishable and we conclude that cluster chondrite chondrules are representative of the normal LL chondrule population. Type II chondrules are depleted in MgO, Al2O3 and refractory lithophiles (REE, Zr, Hf) by factors between 0.65 and 0.79 compared to type I chondrules. The chondrule REE patterns are basically flat with slight LREE < HREE fractionations. Many chondrules exhibit negative Eu anomalies while matrix shows a complementary pattern. Chondrules scatter along a correlation line with a slope of 0.63 in the oxygen 3-isotope diagram, interpreted as the result of O-isotope exchange between chondrule melts and 18O-rich nebular components. In one clast, a distinct anticorrelation between chondrule size and δ18O is found, which may indicate a more intense oxygen isotope exchange by smaller chondrules. In some clasts the δ18O values of type I chondrules are correlated with concentrations of SiO2 and MnO and anticorrelated with MgO, possibly due to the admixture of a SiO2- and MnO-rich component to chondrule melts during oxygen isotope exchange. Two chondrules with negative anomalies in Sm, Eu, and Yb were found and may relate their precursors to refractory material known from group III CAIs. Furthermore, three chondrules with strong LREE > HREE and Zr/Hf fractionations were detected, whose formation history remains to be explained.

  15. Probing the homogeneity of the isotopic composition and molar mass of the ‘Avogadro’-crystal

    NASA Astrophysics Data System (ADS)

    Pramann, Axel; Lee, Kyoung-Seok; Noordmann, Janine; Rienitz, Olaf

    2015-12-01

    Improved measurements on silicon crystal samples highly enriched in the 28Si isotope (known as ‘Si28’ or AVO28 crystal material) have been carried out at PTB to investigate local isotopic variations in the original crystal. This material was used for the determination of the Avogadro constant NA and therefore plays an important role in the upcoming redefinition of the SI units kilogram and mole, using fundamental constants. Subsamples of the original crystal have been extensively studied over the past few years at the National Research Council (NRC, Canada), the National Metrology Institute of Japan (NMIJ, Japan), the National Institute of Standards and Technology (NIST, USA), the National Institute of Metrology (NIM, People’s Republic of China), and multiple times at PTB. In this study, four to five discrete, but adjacent samples were taken from three distinct axial positions of the crystal to obtain a more systematic and comprehensive understanding of the distribution of the isotopic composition and molar mass throughout the crystal. Moreover, improved state-of-the-art techniques in the experimental measurements as well as the evaluation approach and the determination of the calibration factors were utilized. The average molar mass of the measured samples is M  =  27.976 970 12(12) g mol-1 with a relative combined uncertainty uc,rel(M)  =  4.4 ×10-9. This value is in astounding agreement with the values of single samples measured and published by NIST, NMIJ, and PTB. With respect to the associated uncertainties, no significant variations in the molar mass and the isotopic composition as a function of the sample position in the boule were observed and thus could not be traced back to an inherent property of the crystal. This means that the crystal is not only ‘homogeneous’ with respect to molar mass but also has predominantly homogeneous distribution of the three stable Si isotopes.

  16. Longterm and seasonal variation in the isotopic composition of tropospheric CFC-12 and CFC-11

    NASA Astrophysics Data System (ADS)

    Bahlmann, Enno; Weinberg, Ingo; Eckhardt, Tim; Michaelis, Walter; Seifert, Richard

    2013-04-01

    Strong carbon isotope fractionation effects were recently discovered for the degradation of chlorofluorocarbons (CFC's) in landfills and for their photolytical destruction in the troposphere. Both results suggest an enrichment in 13C in the residual fraction of these compounds over time. Thus the isotopic composition of these CFC's may improve our understanding of their fate and reduce uncertainties in current source estimates. Here we report carbon isotope ratios for CFC-11 (CFCl3) and CFC-12 (CF2Cl2)) in background air. The samples were taken during five sampling campaigns between September 2010 and July 2012 with the sample locations spanning from 10°N to 60°N. For CFC-12 our data indicate a long term 13C enrichment of 0.5‰ per year corrobating very recent results from firn air measurements. The long term enrichment is superimposed by a seasonal cycle with an amplitude of 1.2‰ with the most enriched δ13C values occurring in June /July. We hypothesize the long term trend and the seasonal cycle to be driven by the stratosphere troposphere exchange (STE) of CFC-12. The mean δ13C for CFC-11 was -28.4 ± 0.6‰ (n =82) without any significant spatial or temporal variation. The kinetic isotope effect for the photolytic degradation of CFC-11 in the stratosphere is substantially smaller as compared to that for CFC-12 resulting in a minor imprint of the STE on the isotopic composition of tropospheric CFC-11. Furthermore, in contrast to CFC-12, degradation of CFC-11 has been reported from a variety of oxygen deficient marine settings. This may result in small scale variations in the δ13C of tropospheric CFC-11 superimposing any seasonal variability.

  17. Correction of NPL-2013 estimate of the Boltzmann constant for argon isotopic composition and thermal conductivity

    NASA Astrophysics Data System (ADS)

    de Podesta, Michael; Yang, Inseok; Mark, Darren F.; Underwood, Robin; Sutton, Gavin; Machin, Graham

    2015-10-01

    In 2013, a team from NPL, Cranfield University and SUERC published an estimate of the Boltzmann constant based on precision measurements of the speed of sound in argon. A key component of our results was an estimate of the molar mass of the argon gas used in our measurements. To achieve this we made precision comparison measurements of the isotope ratios found in our experimental argon against the ratios of argon isotopes found in atmospheric air. We then used a previous measurement of the atmospheric argon isotope ratios to calibrate the relative sensitivity of the mass spectrometer to different argon isotopes. The previous measurement of the atmospheric argon isotope ratios was carried out at KRISS using a mass spectrometer calibrated using argon samples of known isotopic composition, which had been prepared gravimetrically. We report here a new measurement made at KRISS in October 2014, which directly compared a sample of our experimental gas against the same gravimetrically-prepared argon samples. We consider that this direct comparison has to take precedence over our previous more indirect comparison. This measurement implies a molar mass which is 2.73(60) parts in 106 lighter than our 2013 estimate, a shift which is seven times our 2013 estimate of the uncertainty in the molar mass. In this paper we review the procedures used in our 2013 estimate of molar mass; describe the 2014 measurement; highlight some questions raised by the large change in our estimate of molar mass; and describe how we intend to address the inconsistencies between them. We also consider the effect of a new estimate of the low pressure thermal conductivity of argon at 273.16 K. Finally we report our new best estimate of the Boltzmann constant with revised uncertainty, taking account of the new estimates for the molar mass and the thermal conductivity of the argon.

  18. Discrimination of the Cigarettes Geographical Origin by DRC-ICP-MS Measurements of Pb Isotope Compositions

    NASA Astrophysics Data System (ADS)

    Guo, W.; Hu, S.; Jin, L.

    2014-12-01

    Trace Pb are taken up with the same isotopic ratios as is present in the source soil, and the isotopic composition of Pb could used to reflect these sources and provide powerful indicators of the geographic origin of agriculture products derived from vegetative matter. We developed a simple and high throughput method, which based on DRC-ICP-MS for determination of Pb isotope ratios for discriminating the geographic origin of cigarettes. After acid digestion procedure, the cigarette digested solutions were directly analyzed by ICP-QMS with a DRC pressurized by the non-reactive gas Ne. In the DRC, Ne molecules collision with Pb ions and improves Pb isotope ratios precision 3-fold, which may be due to the collisional dampling smoothes out the ion beam fluctuations. Under the optimum DRC rejection parameter Q (RPq = 0.45), the main matrix components (K, Na, Ca, Mg, Al, Fe etc.) originating from cigarettes were filtered out. Mass discrimination of 208Pb/206Pb ratio in Ne DRC mode increased 0.3% compared to the standard mode, the mass bias due to the in-cell Ne gas collision can be accurately corrected by NIST 981 Pb isotope standard. This method was verified by a tobacco reference material CTV-OTL-2. Results of 208Pb/206Pb and 207Pb/206Pb were 2.0848 ± 0.0028 (2δ) and 0.8452 ± 0.0011 (2δ) for CTA-VTL-2, which were agreed with the literature values (208Pb/206Pb = 2.0884 ± 0.0090 and 207Pb/206Pb = 0.8442 ± 0.0032). The precision of Pb isotope ratios (208Pb/206Pb and 207Pb/206Pb) for the cigarette samples are ranged from 0.01 to 0.08% (N = 5). It has sufficient precision to discriminate 91 different brand cigarettes originated from four different geographic regions (Shown in Fig).

  19. Isotopic Composition of the Neolithic Alpine Iceman's Tooth Enamel and Clues to his Origin

    NASA Astrophysics Data System (ADS)

    Muller, W.; Muller, W.; Halliday, A. N.

    2001-12-01

    Five small enamel fragments from three teeth of the upper right jaw from the mummy of the Neolithic Alpine Iceman have been investigated for their isotopic composition in order to shed light on his geographic origins. Soils from approximately contemporaneous sites were sampled for comparison. Tooth enamel forms ontogenetically very early and is not re-mineralized during later lifetime (unlike with bone material). Therefore, unique insights into the Iceman's childhood can be acquired. Enamel also is the densest tissue of a human body and is thus less susceptible to post-mortem alteration. Both radiogenic (Sr, Pb, Nd) and stable isotopes (O, C) are investigated. Radiogenic isotopes allow reconstruction of the local geological background, because humans incorporate Sr, Pb and Nd from their local environment by eating local food. Stable isotopes provide information about altitude and/or position relative to the main Alpine watershed. High spatial-resolution laser-ablation ICPMS profiles reveal that most elements are distributed in a manner that is essentially similar to modern human teeth except of that La, Ce, Nd (LREE) show up to a 100-fold enrichment towards the outer enamel surface. These uptake-profiles may reflect interaction with melt water, consistent with data for the composition of samples of the Iceman's skin. Biogenic apatites (enamel, bone) have very low in-vivo LREE concentrations, but take up LREEs post-mortem from the burial environment. Ice core samples from the finding site show concentrations up to 400 ppt Ce. Such high uptake of the LREEs precludes the derivation of an in-vivo Nd isotopic signal, but both other radiogenic tracers, Sr and Pb, show pristine (in-vivo) concentrations of 87 ppm and 0.1 ppm, respectively. Strontium isotopic compositions were determined on fragments from the canine, the first and second premolar (1 - 9 mg) and two hip bone samples, utilizing three sequential leaching steps for each sample to detect possible alteration

  20. Sulfur Isotopic Composition of Ocean Island Basalts: New insights into the composition of the primitive mantle and mantle recycling.

    NASA Astrophysics Data System (ADS)

    Dottin, J. W., III; Labidi, J.; Jackson, M. G.; Farquhar, J.

    2015-12-01

    Here, we report the S isotopic composition of bulk sulfide inclusions in olivine and pyroxene isolated from lavas originating from 11 oceanic hotspot volcanoes, including Hawaii, Samoa, Pitcairn, and Mangaia. We also report the S isotopic composition of a peridotite xenolith from a Hawaiian lava. We digested between 200 and 1500 mg of sample using an HF chemical extraction technique (Labidi et al., 2012) and analyzed for S isotopes on a Thermo-Finnigan MAT 235 IRMS. A total of 35 samples from 11 different islands were analyzed, but only 14 samples yielded sufficient S for analysis. S concentrations range between 22 and 555 ppm S (±10%) in magmatic olivines and pyroxenes from Mangaia. We extracted 47 ppm S from the Hawaiian xenolith. For Mangaia, δ34S values range between -4.90±0.20‰ and +0.42±0.20‰, and Δ33S values range between +0.001±0.008‰ and +0.044±0.008‰. Δ36S values range between -0.03±0.20‰ and +0.32±0.20‰ (all 1σ). We measured 20 ppm S in the Baffin Island olivine separate. We observe a δ34S value of -1.97±0.20‰ and a Δ33S value of +0.010±0.008‰ in this sample. This lava may tap into the most primitive mantle source, based on the primordial He isotopic composition of this locality. Therefore, our S isotopic data suggest a sub-chondritic δ34S value for the primitive mantle, in agreement with results from Labidi et al. (2014). Mangaia and Baffin phenocrysts are observed to host significant S amounts. However, samples from Pitcairn, Samoa, Hawaii, and others, all show S contents < 5 ppm S. This suggests negligible sulfide saturation for their host lavas. Lastly, we observe mass-dependent S isotope ratios for all Mangaia samples investigated here (n=8), inconsistent with the Cabral et al. (2013) report. However, we did not analyze the same samples from Mangaia. A lack of MIF in our sample suite may be attributed to: 1. Heterogeneities within the same hotspot and 2. Dilutions of the MIF signature when a single sulfide may contain

  1. Hydrogen isotopic composition of individual n-alkanes as an intrinsic tracer for bioremediation and source identification of petroleum contamination.

    PubMed

    Pond, Kristy L; Huang, Yongsong; Wang, Yi; Kulpa, Charles F

    2002-02-15

    The isotopic signatures of crude oil hydrocarbons are potentially powerful intrinsic tracers to their origins and the processes by which the oils are modified in the environment. Stable carbon isotopic data are of limited use for studying petroleum contaminants because of the relatively small amount of isotopic fractionation that occurs during natural processes. Hydrogen isotopes, in contrast, are commonly fractionated to a much greater extent and as a result display larger variations in delta values. We studied the effect of in vitro aerobic biodegradation on the hydrogen isotopic composition of individual n-alkanes from crude oil. The isotopic analysis was conducted using gas chromatography-thermal conversion-isotope ratio mass spectrometry. In general, biodegradation rates decreased with increasing hydrocarbon chain length, consistent with previous studies. More importantly the n-alkanes that were degraded at the fastest rates (n-C15 to n-C18) also showed the largest overall isotopic fractionation (approximately 12-25 per thousand deuterium enrichment), suggesting that the lower molecular weight n-alkanes can be used to monitor in-situ bioremediation of crude oil contamination. The hydrogen isotopic compositions of the longer chain alkanes (n-C19 to n-C27) were relatively stable during biodegradation (<5%o overall deuterium enrichment), indicating that these compounds are effective tracers for oil-source identification studies.

  2. The stable isotope compositions of mercury in atmospheric particles (PM10) from Paris (France) and vicinity

    NASA Astrophysics Data System (ADS)

    Widory, D.; Petelet-Giraud, E.; Johnson, T.; Quétel, C.; Snell, J.; van Bocxstaele, M.; Bullen, T. D.

    2010-12-01

    Solid mercury (Hg) in atmospheric particles in the environment can be derived from a variety of primary sources and cycled through numerous secondary processes, complicating identification of its origin. Using the PM10 fraction of aerosols from Paris and vicinity, we investigated the possibility that Hg stable isotope compositions could help identify the origins of atmospheric Hg and processes affecting the atmospheric Hg budget. Characterization of Hg isotope compositions of emissions from the different potential sources (e.g. waste incinerators, coal-fired power plants, metal refining plants, road traffic, heating sources and volcanic gases) shows that those containing Hg are clearly discriminated by specific Hg isotope signatures. PM10 were sampled in three different locations: A) downtown Paris, characterized by diffuse pollution, B) nearby suburb of the city, close to suspected Hg emitters, and C) in distant suburb of the city, having only a few industrial activities in the area. Results indicate that Hg in most of the PM10 samples is explained by binary mixings. The mixing end-members include at least two distinct sources at low Hg concentrations in the aerosols, compatible with industrial activity. At high Hg concentration in the aerosols, the isotopes may likewise indicate two distinct sources with δ202Hg compositions of -4.1 and -11.4 ‰. This range is significantly less than that measured on the potential sources of Hg pollution, and may indicate secondary processes, such as gas to solid phase transfers. The occurrence of post-emission processes is reinforced by the strong correlations existing between these low δ202Hg and MIF Δ201Hg values.

  3. New perspectives on the Li isotopic composition of the upper continental crust and its weathering signature

    NASA Astrophysics Data System (ADS)

    Sauzéat, Lucie; Rudnick, Roberta L.; Chauvel, Catherine; Garçon, Marion; Tang, Ming

    2015-10-01

    Lithium isotopes are increasingly used to trace both present-day and past weathering processes at the surface of the Earth, and could potentially be used to evaluate the average degree of past weathering recorded by the upper continental crust (UCC). Yet the previous estimate of average δ7Li of the UCC has a rather large uncertainty, hindering the use of Li isotopes for this purpose. New δ7Li for desert and periglacial loess deposits (windblown dust) from several parts of the world (Europe, Argentina, China and Tajikistan) demonstrate that the former are more homogeneous than the latter, and may therefore serve as excellent proxies of the average composition of large tracts of the UCC. The Li isotopic compositions and concentrations of desert loess samples are controlled by eolian sorting that can be quantified by a binary mixing between a weathered, fine-grained end-member, dominated by phyllosilicates and having low δ7Li, and an unweathered, coarse-grained end-member, that is a mixture of quartz and plagioclase having higher δ7Li. We use correlations between insoluble elements (REE, Nd/Hf and Fe2O3/SiO2), Li concentrations (henceforth referred as [Li]), and δ7Li to estimate a new, more precise, average Li isotopic composition and concentration for the UCC: [ Li ] = 30.5 ± 3.6 (2 σ) ppm, and δ7Li = + 0.6 ± 0.6 (2 σ). The δ7Li for desert loess deposits is anti-correlated with the chemical index of alteration (CIA). Using this relationship, along with our average δ7Li, we infer that (1) the present-day CIA of the average UCC is 61-2+4 (2 σ), higher than the common reference value of 53, and (2) the average proportion of chemically weathered components is as high as 37-10+17 (2 σ)% at the surface of the Earth.

  4. Amino acid compositions in heated carbonaceous chondrites and their compound-specific nitrogen isotopic ratios

    NASA Astrophysics Data System (ADS)

    Chan, Queenie Hoi Shan; Chikaraishi, Yoshito; Takano, Yoshinori; Ogawa, Nanako O.; Ohkouchi, Naohiko

    2016-01-01

    A novel method has been developed for compound-specific nitrogen isotope compositions with an achiral column which was previously shown to offer high precision for nitrogen isotopic analysis. We applied the method to determine the amino acid contents and stable nitrogen isotopic compositions of individual amino acids from the thermally metamorphosed (above 500 °C) Antarctic carbonaceous chondrites Ivuna-like (CI)1 (or CI-like) Yamato (Y) 980115 and Ornans-like (CO)3.5 Allan Hills (ALH) A77003 with the use of gas chromatography/combustion/isotope ratio mass spectrometry. ALHA77003 was deprived of amino acids due to its extended thermal alteration history. Amino acids were unambiguously identified in Y-980115, and the δ15N values of selected amino acids (glycine +144.8 ‰; α-alanine +121.2 ‰) are clearly extraterrestrial. Y-980115 has experienced an extended period of aqueous alteration as indicated by the presence of hydrous mineral phases. It has also been exposed to at least one post-hydration short-lived thermal metamorphism. Glycine and alanine were possibly produced shortly after the accretion event of the asteroid parent body during the course of an extensive aqueous alteration event and have abstained from the short-term post-aqueous alteration heating due to the heterogeneity of the parent body composition and porosity. These carbonaceous chondrite samples are good analogs that offer important insights into the target asteroid Ryugu of the Hayabusa-2 mission, which is a C-type asteroid likely composed of heterogeneous materials including hydrated and dehydrated minerals.

  5. Isotopic Composition of Trapped and Cosmogenic Noble Gases in Several Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Garrison, Daniel H.; Bogard, Donald D.

    1997-01-01

    Isotopic abundances of the noble gases were measured in the following Martian meteorites: two shock glass inclusions from EET79001, shock vein glass from Shergotty and Y793605, and whole rock samples of ALH84001 and QUE94201. These glass samples, when combined with literature data on a separate single glass inclusion from EET79001 and a glass vein from Zagami, permit examination of the isotopic composition of Ne, Ar, Kr, and Xe trapped from the Martian atmosphere in greater detail. The isotopic composition of Martian Ne, if actually present in these glasses, remains poorly defined. The Ar-40/Ar-36 ratio of Martian atmospheric Ar may be much less than the ratio measured by Viking and possibly as low as approx. 1900. The atmospheric Ar-36/Ar-38 ratio is less than or equal to 4.0. Martian atmospheric Kr appears to be enriched in lighter isotopes by approx. 0.4%/amu compared to both solar wind Kr and to the Martian composition previously reported. The Martian atmospheric Ar-36/Xe-132 and Kr-84/Xe-132 Xe elemental ratios are higher than those reported by Viking by factors of approx. 3.3 and approx. 2.5, respectively. Cosmogenic gases indicate space exposure ages of 13.9 +/- 1 Myr for ALH84001 and 2.7 +/- 0.6 Myr for QUE94201. Small amounts of Ne-21 produced by energetic solar protons may be present in QUE94201, but are not present in ALH84001 or Y793605. The space exposure age for Y793605 is 4.9 +/- 0.6 Myr and appears to be distinctly older than the ages for basaltic shergottites.

  6. Variability in isotopic composition of base flow in two headwater streams of the southern Appalachians

    NASA Astrophysics Data System (ADS)

    Singh, Nitin K.; Emanuel, Ryan E.; McGlynn, Brian L.

    2016-06-01

    We investigated the influence of hillslope scale topographic characteristics and the relative position of hillslopes along streams (i.e., internal catchment structure) on the isotopic composition of base flow in first-order, forested headwater streams at Coweeta Hydrologic Laboratory. The study focused on two adjacent forested catchments with different topographic characteristics. We used stable isotopes (18O and 2H) of water together with stream gauging and geospatial analysis to evaluate relationships between internal catchment structure and the spatiotemporal variability of base flow δ18O. Base flow δ18O was variable in space and time along streams, and the temporal variability of base flow δ18O declined with increasing drainage area. Base flow became enriched in 18O moving along streams from channel heads to catchment outlets but the frequency of enrichment varied between catchments. The spatiotemporal variability in base flow δ18O was high adjacent to large hillslopes with short flow paths, and it was positively correlated with the relative arrangement of hillslopes within the catchment. These results point to influence of unique arrangement of hillslopes on the patterns of downstream enrichment. Spatial variability in base flow δ18O within the streams was relatively low during dry and wet conditions, but it was higher during the transition period between dry and wet conditions. These results suggest that the strength of topographic control on the isotopic composition of base flow can vary with catchment wetness. This study highlights that topographic control on base flow generation and isotopic composition is important even at fine spatial scales.

  7. Interpreting the Calcium Isotopic Composition of Seawater Through the Neogene and Quaternary

    NASA Astrophysics Data System (ADS)

    de La Rocha, C. L.; Sime, N. G.; Tipper, E. T.; Tripati, A.; Galy, A.; Bickle, M. J.

    2006-12-01

    It has been proposed that the calcium isotopic composition (δ^{44/42}Ca) of marine biogenic carbonates can be used to reconstruct past changes in the Ca2+ content of the ocean, lending insight into in weathering fluxes of Ca to the oceans and atmospheric concentrations of CO2. Here we present a 20 million year record of the δ^{44/42}Ca of planktonic foraminifera from ODP site 925, in the Atlantic Ocean (Ceara Rise), and make a critical analysis of Ca isotope-based reconstructions of the Ca cycle. The Ceara Rise record, whose δ^{44/42}Ca averages +0.37 ± 0.05 (1σ S.D.) and ranges from +0.21 ‰ to +0.52 ‰, is a good match to previously published Neogene Ca isotope records based on foraminifera, but differs from the record based on bulk carbonates which has values that are as much as 0.25 ‰ lower. Bulk carbonate and planktonic foraminfera from core tops differ only by 0.06 ± 0.06 ‰ (n =5), leaving room for additional factors than potentially differing fractionation factors for the production of calcite by foraminifera and coccolithophorids to cause discrepancy between bulk carbonate and foraminiferan values back through time. Modeling the global Ca cycle from downcore variations in δ^{44/42}Ca by assuming fixed values for the isotopic composition of weathering inputs (δ^{44/42}Caw) and for isotope fractionation associated with the production of carbonate sediments (Δsed) results in large variations in the mass of Ca2+ in the oceans during the Neogene. This suggests that δ^{44/42}Caw and Δsed instead fluctuate over time. Ca isotope fractionation during weathering processes, such as has been recently documented, could easily result in variations in δ^{44/42}Caw of a few tenths of permil associated with shifts in climate on land. Likewise the differing degree of isotope fractionation associated with aragonite versus calcite formation could drive shifts in Δsed of several tenths of permil with changes in the Mg/Ca of seawater or the relative importance

  8. A thirty year record of the isotopic composition of atmospheric methane from North America

    NASA Astrophysics Data System (ADS)

    Rice, A. L.; Teama, D. G.; Roeger, F. H.; Butenhoff, C. L.; Khalil, A. K.

    2012-12-01

    Methane (CH4) is one of the most important greenhouse gases after water vapor and carbon dioxide. Its atmospheric concentration increased from 650 ppb during the preindustrial era to nearly 1800 ppb in the present day due to human activities such as rice cultivation, animal husbandry, biomass burning, and fossil fuel production and use. Since the 1980s, the long-term growth rate of atmospheric CH4 slowed dramatically consistent with a leveling off of CH4 sources with significant interannual variability over this period. One powerful tool to constrain changes in sources and sinks is the use of stable isotopes of atmospheric CH4 because of the distinct values of carbon isotope (δ13C) and hydrogen isotope (δD) ratios in CH4 sources and characteristic isotopic fractionation effects in sinks. Measurements of the long-term trend of the isotopic composition of CH4 can improve the constraint of changes to the CH4 budget from microbial sources (e.g., wetlands, ruminants, and rice agriculture, δ13C ~-60 ‰, δD ~-300‰), fossil sources (e.g. natural gas and coal mining, δ13C ~-40‰, δD ~-200‰), and biomass burning (δ13C ~-25‰, δD ~-100‰). In this work, we present measurements of δ13C and δD of atmospheric CH4 from a unique archive of more than 200 air samples collected at Cape Meares, Oregon (45.5°N, 124°W) from 1978 to 1998. The measurements from this archive indicate enrichments in both isotope tracers over this period which average 0.017 (±0.002) ‰yr-1 for δ13C and 0.68 (±0.04) ‰yr-1 for δD. Seasonal cycles in δ13C and δD are also evident with amplitudes of ~ 0.3 ‰ and ~ 4 ‰, respectively; maximum values are found May-July and minimum values September-December, consistent with previous results from the mid-latitude northern hemisphere. Combining our results with more recent timeseries since 1988 from Olympic Peninsula (WA, 48°N), Montana de Oro (CA, 35°N), and Niwot Ridge (CO, 40°N) provides a composite record of the isotopic

  9. Measurement of position-specific 13C isotopic composition of propane at the nanomole level

    NASA Astrophysics Data System (ADS)

    Gilbert, Alexis; Yamada, Keita; Suda, Konomi; Ueno, Yuichiro; Yoshida, Naohiro

    2016-03-01

    We have developed a novel method for analyzing intramolecular carbon isotopic distribution of propane as a potential new tracer of its origin. The method is based on on-line pyrolysis of propane followed by analysis of carbon isotope ratios of the pyrolytic products methane, ethylene and ethane. Using propane samples spiked with 13C at the terminal methyl carbon, we characterize the origin of the pyrolytic fragments. We show that the exchange between C-atoms during the pyrolytic process is negligible, and thus that relative intramolecular isotope composition can be calculated. Preliminary data from 3 samples show that site-preference (SP) values, defined as the difference of δ13C values between terminal and sub-terminal C-atom positions of propane, range from -1.8‰ to -12.9‰. In addition, SP value obtained using our method for a thermogenic natural gas sample is consistent with that expected from theoretical models of thermal cracking, suggesting that the isotope fractionation associated with propane pyrolysis is negligible. The method will provide novel insights into the characterization of the origin of propane and will help better understand the biogeochemistry of natural gas deposits.

  10. Uranium isotope composition of a laterite profile during extreme weathering of basalt in Guangdong, South China

    NASA Astrophysics Data System (ADS)

    Huang, J.; Zhou, Z.; Gong, Y.; Lundstrom, C.; Huang, F.

    2015-12-01

    Rock weathering and soil formation in the critical zone are important for material cycle from the solid Earth to superficial system. Laterite is a major type of soil in South China forming at hot-humid climate, which has strong effect on the global uranium cycle. Uranium is closely related to the environmental redox condition because U is stable at U(Ⅳ) in anoxic condition and U(Ⅵ) as soluble uranyl ion (UO22+) under oxic circumstance. In order to understand the behavior of U isotopes during crust weathering, here we report uranium isotopic compositions of soil and base rock samples from a laterite profile originated from extreme weathering of basalt in Guangdong, South China. The uranium isotopic data were measured on a Nu Plasma MC-ICP-MS at the University of Illinois at Urbana-Champaign using the double spike method. The δ238U of BCR-1 is -0.29±0.03‰ (relative to the international standard CRM-112A), corresponding to a 238U/235U ratio of 137.911±0.004. Our result of BCR-1 agrees with previous analyses (e.g., -0.28‰ in Weyer et al. 2008) [1]. U contents of the laterite profile decrease from 1.9 ppm to 0.9 ppm with depth, and peak at 160 - 170 cm (2.3 ppm), much higher than the U content of base rocks (~0.5 ppm). In contrary, U/Th of laterites is lower than that of base rock (0.27) except the peak at the depth of 160-170 cm (0.38), indicating significant U loss during weathering. Notably, U isotope compositions of soils show a small variation from -0.38 to -0.28‰, consistent with the base rock within analytical error (0.05‰ to 0.08‰, 2sd). Such small variation can be explained by a "rind effect" (Wang et al., 2015) [2], by which U(Ⅳ) can be completely oxidized to U(VI) layer by layer during basalt weathering by dissolved oxygen. Therefore, our study indicates that U loss during basalt weathering at the hot-humid climate does not change U isotope composition of superficial water system. [1] Weyer S. et al. (2008) Natural fractionation of 238U/235

  11. Laboratory and Field Measurements of the Nitrogen Isotopic Composition of NOx

    NASA Astrophysics Data System (ADS)

    Fibiger, D. L.; Miller, D. J.; Dahal, B. R.; Lew, A. F.; Peltier, R.; Hastings, M. G.

    2014-12-01

    The nitrogen isotopic composition of nitrogen oxides (NOx = NO + NO2) has been measured from several NOx emissions sources in prior studies. These measurements have utilized a variety of methods for collecting the NOx as nitrate or nitrite for isotopic analysis, but none of these methods have been verified for complete conversion of NOx. Less than 100% conversion can result in isotopic fractionations. We present a method for accurately measuring the nitrogen isotopic composition of NOx using a .25 M KMnO4 and 0.5 M NaOH solution. Based on laboratory tests, this technique has been found to collect all NOx passed through under a variety of conditions (e.g., air flow rate, NOx concentration, temperature, humidity), allowing for diagnosis of δ15N-NOx without correction for fractionation. The precision across the entire analytic technique is 1.5‰. This active collection method is advantageous for collecting NOx over short time scales in environments with highly variable NOx sources and concentrations. The major drawback of the NaOH/KMnO4 method is a significant nitrate background found in the KMnO4, but this background is consistent and can be easily accounted for. We aim to use this method to provide more robust constraints on the isotopic signatures of NOx emissions from different sources. Initial results will be presented from lab- and field-based collections of NOx emissions. Emissions from a diesel engine were measured in a laboratory smog chamber and yielded δ15N values with a mean of -18.0‰ (n = 5, 1σ = 0.97‰). Measurements of δ15N-NOx were also made on a rooftop between two highways in Providence, RI. The values ranged from -7.7 to -0.63‰ for different time periods sampled, with excellent reproducibility in side-by-side collections. Additionally, the NaOH/KMnO4 was deployed in a laboratory study of biomass burning (FLAME4) to analyze the nitrogen isotopic composition of NOx produced from the burning of variety of materials (e.g. trees, agricultural

  12. Investigating the source, transport, and isotope composition of water vapor in the planetary boundary layer

    DOE PAGES

    Griffis, Timothy J.; Wood, Jeffrey D.; Baker, John M.; ...

    2016-04-25

    Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle – an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understand feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor at a very tall tower (185 m) in the upper Midwest, United States, to diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotopemore » observations for this region. Several simple isotope models and cross-wavelet analyses were used to assess the importance of the Rayleigh distillation process, evaporation, and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a large seasonal amplitude (mean monthly δ18Ov ranged from –40.2 to –15.9 ‰ and δ2Hv ranged from –278.7 to –113.0 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio when considering the entire hourly data set. However, this relation was strongly modulated by evaporation and PBL entrainment processes at timescales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess (dv) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that evaporation often leads changes in dv, confirming that it is a potential tracer of regional evaporation. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional evaporation. However, isoforcing calculations and mixing model analyses for high PBL water vapor mixing ratio events ( > 25 mmol mol–1) indicate that regional

  13. Stable isotope composition of land snail body water and its relation to environmental waters and shell carbonate

    SciTech Connect

    Goodfriend, G.A.; Magaritz, M.; Gat, J.R. )

    1989-12-01

    Day-to-day and within-day (diel) variations in {delta}D and {delta}{sup 18}O of the body water of the land snail, Theba pisana, were studied at a site in the southern coastal plain of Israel. Three phases of variation, which relate to isotopic changes in atmospheric water vapor, were distinguished. The isotopic variations can be explained by isotopic equilibration with atmospheric water vapor and/or uptake of dew derived therefrom. During the winter, when the snails are active, there is only very minor enrichment in {sup 18}O relative to equilibrium with water vapor or dew, apparently as a result of metabolic activity. But this enrichment becomes pronounced after long periods of inactivity. Within-day variation in body water isotopic composition is minor on non-rain days. Shell carbonate is enriched in {sup 18}O by ca. 1-2% relative to equilibrium with body water. In most regions, the isotopic composition of atmospheric water vapor (or dew) is a direct function of that of rain. Because the isotopic composition of snail body water is related to that of atmospheric water vapor and the isotopic composition of shell carbonate in turn is related to that of body water, land snail shell carbonate {sup 18}O should provide a reliable indication of rainfall {sup 18}O. However, local environmental conditions and the ecological properties of the snail species must be taken into account.

  14. Comparison of Modeled and Observed Environmental Influences on the Stable Oxygen and Hydrogen Isotope Composition of Leaf Water in Phaseolus vulgaris L. 1

    PubMed Central

    Flanagan, Lawrence B.; Comstock, Jonathan P.; Ehleringer, James R.

    1991-01-01

    In this paper we describe how a model of stable isotope fractionation processes, originally developed by H. Craig and L. I. Gordon ([1965] in E Tongiorgi, ed, Proceedings of a Conference on Stable Isotopes in Oceanographic Studies and Paleotemperature, Spoleto, Italy, pp 9-130) for evaporation of water from the ocean, can be applied to leaf transpiration. The original model was modified to account for turbulent conditions in the leaf boundary layer. Experiments were conducted to test the factors influencing the stable isotopic composition of leaf water under controlled environment conditions. At steady state, the observed leaf water isotopic composition was enriched above that of stem water with the extent of the enrichment dependent on the leaf-air vapor pressure difference (VPD) and the isotopic composition of atmospheric water vapor (AWV). The higher the VPD, the larger was the observed heavy isotope content of leaf water. At a constant VPD, leaf water was relatively depleted in heavy isotopes when exposed to AWV with a low heavy isotope composition, and leaf water was relatively enriched in heavy isotopes when exposed to AWV with a large heavy isotope composition. However, the observed heavy isotope composition of leaf water was always less than that predicted by the model. The extent of the discrepancy between the modeled and observed leaf water isotopic composition was a strong linear function of the leaf transpiration rate. PMID:16668226

  15. Iron isotopic compositions of adakitic and non-adakitic granitic magmas: Magma compositional control and subtle residual garnet effect

    NASA Astrophysics Data System (ADS)

    He, Yongsheng; Wu, Hongjie; Ke, Shan; Liu, Sheng-Ao; Wang, Qiang

    2017-04-01

    Here we present iron (Fe) isotopic compositions of 51 well-characterized adakitic and non-adakitic igneous rocks from the Dabie orogen, Central China and Panama/Costa Rica, Central America. Twelve I-type non-adakitic granitoid samples from the Dabie orogen yield δ56Fe ranging from -0.015‰ to 0.184‰. The good correlations between δ56Fe and indices of magma differentiation (e.g., SiO2, FeOt, Mg#, and Fe3+/ΣFe) suggest Fe2+-rich silicate and oxide minerals dominated fractional crystallization with Δ56Femelt-crystal ∼ 0.06‰ may account for the δ56Fe variation in these samples. One A-type granite sample from the Dabie orogen has δ56Fe as high as 0.447‰, likely indicating less magnetite crystallization and an increase in 103lnβmelt with magma (Na + K)/(Ca + Mg). Combined with the literature data, most high silica (SiO2 ⩾ 71 wt.%) granitic rocks define a good positive linear correlation between δ56Fe and (Na + K)/(Ca + Mg): δ56Fe = 0.0062‰ × (Na + K)/(Ca + Mg) + 0.130‰ (R2 = 0.66). Given that fractional crystallization also tends to increase δ56Fe with (Na + K)/(Ca + Mg), this correlation can serve as the maximum estimate of the magma compositional control on Fe isotope fractionation. Low-Mg adakitic samples (LMA) have δ56Fe ranging from 0.114‰ to 0.253‰. The melt compositional control on LMA δ56Fe could be insignificant due to their limited (Na + K)/(Ca + Mg) variation. Except for one sample that may be affected by late differentiation, 14 out of 15 LMA have δ56Fe increasing with (Dy/Yb)N, reflecting a subtle but significant effect of residual garnet proportion. This serves as evidence for that source mineralogy may play an important role in fractionating Fe isotopes during partial melting. Dabie and Central America high-Mg adakitic samples have homogeneous Fe isotopic compositions with mean δ56Fe of 0.098 ± 0.038‰ (2SD, N = 11) and 0.085 ± 0.045‰ (2SD, N = 11), respectively. These samples have undergone melt-mantle interaction

  16. Monitoring of carbon isotope composition of snow cover for Tomsk region

    NASA Astrophysics Data System (ADS)

    Akulov, P. A.; Volkov, Y. V.; Kalashnikova, D. A.; Markelova, A. N.; Melkov, V. N.; Simonova, G. V.; Tartakovskiy, V. A.

    2016-11-01

    This article shows the potential of using δ13C values of pollutants in snow pack to study the human impact on the environment of Tomsk and its surroundings. We believe that it is possible to use a relation between the isotope compositions of a fuel and black carbon for establishing the origin of the latter. The main object of our investigation was dust accumulated by the snow pack in the winter of 2015-2016. The study of dust samples included the following steps: determination of the total carbon content in snow pack samples of Tomsk and its surroundings, extraction of black carbon from the dust, as well as the determination of δ13C values of the total and black carbon accumulated in the snow pack. A snow survey was carried out on the 26th of January and on the 18th of March. The relative carbon content in the dust samples was determined by using an EA Flash 2000 element analyzer. It varied from 3 to 24%. The maximum carbon content was in the dust samples from areas of cottage building with individual heating systems. The δ13C values of the total and black carbon were determined by using a DELTA V Advantage isotope mass spectrometer (TomTsKP SB RAS). The isotope composition of black carbon corresponded to that of the original fuel. This fact allowed identifying the origin of black carbon in some areas of Tomsk.

  17. Continental paleothermometry and seasonality using the isotopic composition of aragonitic otoliths of freshwater fishes

    NASA Astrophysics Data System (ADS)

    Patterson, William P.; Smith, Gerald R.; Lohmann, Kyger C.

    To investigate the applicability of oxygen isotope themometry using fish aragonite, the δ18O values of paired otolith and water samples were analyzed from six large modem temperate lakes. Otoliths are accretionaiy aragonitic structures which are precipitated within the sacculus of fish ears. Deep-water obligate benthic species from the hypolimnion of the Laurentian Great Lakes of North America and Lake Baikal, Siberia, provided cold-water end member values for aragonite δ18O. Warm-water values were obtained from naturally grown warm-water stenothermic species and from fish grown in aquaria under controlled conditions. These two groups, which represent growth over a temperature range of 3.2-30.3°C. were employed to determine the oxygen isotope temperature fractionation relationship for aragonite-water: 103lnα = 18.56 (±0.319)·(103)T-1 K -33.49 (±0.307). Empirical calibration of a fish aragonite thennometry equation allows its direct application to studies of paleoclimate. For example, high-resolution sampling of shallow-water eurythermic species coupled with a knowledge of the isotopic composition of meteoric waters can be used to determine seasonal temperature variation. This approach was tested using a modem shallow-water eurythermic species from Sandusky Bay, Lake Erie. Temperatures calculated from carbonate composition agree with meteorological records from the Sandusky Bay weather station for the same time period.

  18. The isotopic composition and concentration of Ag in iron meteorites and the origin of exotic silver

    NASA Technical Reports Server (NTRS)

    Kaiser, T.; Wasserburg, G. J.

    1983-01-01

    The isotopic composition of Ag and the concentration of Ag and Pd in Canyon Diablo (IA), Grant (IIIB), Santa Clara, Tlacotepec and Warburton Range (IVB), Pinon and Deep Springs (anom) were analyzed. Troilite from Santa Clara and from Grant was also studied. With the exception of IA, all the meteorites were enriched in Ag-107 by about 2%-212% and the ratio of Ag-107/Ag-109 in the metal phase was found to be greater than the terrestrial value. Ag of anomalous isotopic composition was found to be common in all IVB and anomalous meteorites. A correlation of Ag-107/Ag-109 with Pd/Ag was established except for the iron meteorite of Santa Clara. The excess Ag-107 is thought to result from the decay of Pd-107. The Grant data appear to represent a Pd-107-Ag-107 isochron and indicate that the cooling rate at elevated temperatures was rapid enough to preserve the isotopic differences between metal and troilite. The data suggest that Ag in Santa Clara is made up of almost pure Ag-107 produced from Pd-107 decay and Ag-109 produced by nuclear reactions with only a small amount of 'normal' Ag. This indicates an intense energetic particle bombardment history in the early solar system which occurred after the formation of small planetary bodies.

  19. [Quantitative estimation source of urban atmospheric CO2 by carbon isotope composition].

    PubMed

    Liu, Wei; Wei, Nan-Nan; Wang, Guang-Hua; Yao, Jian; Zeng, You-Shi; Fan, Xue-Bo; Geng, Yan-Hong; Li, Yan

    2012-04-01

    To effectively reduce urban carbon emissions and verify the effectiveness of currently project for urban carbon emission reduction, quantitative estimation sources of urban atmospheric CO2 correctly is necessary. Since little fractionation of carbon isotope exists in the transportation from pollution sources to the receptor, the carbon isotope composition can be used for source apportionment. In the present study, a method was established to quantitatively estimate the source of urban atmospheric CO2 by the carbon isotope composition. Both diurnal and height variations of concentrations of CO2 derived from biomass, vehicle exhaust and coal burning were further determined for atmospheric CO2 in Jiading district of Shanghai. Biomass-derived CO2 accounts for the largest portion of atmospheric CO2. The concentrations of CO2 derived from the coal burning are larger in the night-time (00:00, 04:00 and 20:00) than in the daytime (08:00, 12:00 and 16:00), and increase with the increase of height. Those derived from the vehicle exhaust decrease with the height increase. The diurnal and height variations of sources reflect the emission and transport characteristics of atmospheric CO2 in Jiading district of Shanghai.

  20. The effect of natural weathering on the chemical and isotopic compositions of biotites

    USGS Publications Warehouse

    Clauer, Norbert; O'Neil, J.R.; Bonnot-Courtois, C.

    1982-01-01

    The effect of progressive natural weathering on the isotopic (Rb-Sr, K-Ar, ??D, ??18O) and chemical (REE, H2O+) compositions of biotite has been studied on a suite of migmatitic biotites from the Chad Republic. During the early stages of weathering the Rb-Sr system is strongly affected, the hydrogen and oxygen isotope compositions change markedly, the minerals are depleted in light REE, the water content increases by a factor of two, and the K-Ar system is relatively little disturbed. During intensive weathering the K-Ar system is more strongly disturbed than the Rb-Sr system. Most of the isotopic and chemical modifications take place under nonequilibrium conditions and occur before newly formed kaolinite and/or smectite can be detected. These observations suggest that 1. (a) "protominerals" may form within the biotite structure during the initial period of weathering, and 2. (b) only when chemical equilibrium is approached in the weathering profile are new minerals able to form. ?? 1982.

  1. Elemental and isotopic compositions of noble gases in the mantle: Pete's path

    NASA Astrophysics Data System (ADS)

    Moreira, Manuel; Péron, Sandrine; Colin, Aurélia

    2016-04-01

    Noble gases are tracers of the origin of the volatiles on Earth and other terrestrial planets. The determination of their isotopic compositions in oceanic basalts allows discriminating between different possible scenarios for the origin of volatiles (chondritic, solar, cometary). However, oceanic basalts show a ubiquitous component having atmospheric noble gas compositions, which reflects a shallow air contamination. This component masks the mantle composition and only step crushing is able to (partially) remove it. Nevertheless, the exact mantle composition is always unconstrained due to the uncertainty on its complete removal. Developed by Pete Burnard (Burnard et al., 1997; Burnard, 1999), single vesicle analysis using laser ablation is a challenging technique to determine the mantle composition, free of atmospheric contamination. We have used this technique to measure He, Ne, Ar isotopes and CO2 in single vesicles from both MORB and OIB (Galapagos, Iceland). Vesicles are located using microtomography and the noble gases are measured using the Noblesse mass spectrometer from IPGP using an Excimer laser to open the vesicles. Both Galapagos and Iceland samples show that the 20Ne/22Ne ratio is limited to ~12.8 in the primitive mantle, suggesting that the origin of the light noble gases can be attributed to irradiated material instead of a simple dissolution of solar gases into a magma ocean (Moreira and Charnoz, 2016). Such a scenario of incorporation of light noble gases by irradiation also explains the terrestrial argon isotopic composition. However, the Kr and Xe contribution of implanted solar wind is small and these two noble gases were carried on Earth by chondrites and/or cometary material. Burnard, P., D. Graham and G. Turner (1997). "Vesicle-specific noble gas analyses of « popping rock »: implications for primordial noble gases in the Earth." Science 276: 568-571. Burnard, P. (1999). "The bubble-by-bubble volatile evolution of two mid-ocean ridge

  2. Absolute Summ

    NASA Astrophysics Data System (ADS)

    Phillips, Alfred, Jr.

    Summ means the entirety of the multiverse. It seems clear, from the inflation theories of A. Guth and others, that the creation of many universes is plausible. We argue that Absolute cosmological ideas, not unlike those of I. Newton, may be consistent with dynamic multiverse creations. As suggested in W. Heisenberg's uncertainty principle, and with the Anthropic Principle defended by S. Hawking, et al., human consciousness, buttressed by findings of neuroscience, may have to be considered in our models. Predictability, as A. Einstein realized with Invariants and General Relativity, may be required for new ideas to be part of physics. We present here a two postulate model geared to an Absolute Summ. The seedbed of this work is part of Akhnaton's philosophy (see S. Freud, Moses and Monotheism). Most important, however, is that the structure of human consciousness, manifest in Kenya's Rift Valley 200,000 years ago as Homo sapiens, who were the culmination of the six million year co-creation process of Hominins and Nature in Africa, allows us to do the physics that we do. .

  3. Tracing the secular evolution of the UCC using the iron isotope composition of ancient glacial diamictites

    NASA Astrophysics Data System (ADS)

    Liu, X. M.; Gaschnig, R. M.; Rudnick, R. L.; Hazen, R. M.; Shahar, A.

    2015-12-01

    Iron is the fourth most abundant element in the continental crust and influences global climate and biogeochemical cycles in the ocean1. Continental inputs, including river waters, sediments and atmospheric dust are dominant sources (>95%) of iron into the ocean2. Therefore, understanding how continental inputs may have changed through time is important in understanding the secular evolution of the marine Fe cycle. We analysed the Fe isotopic composition of twenty-four glacial diamictite composites, upper continental crust (UCC) proxies, with ages ranging from the Mesoarchean to the Paleozoic eras to characterize the secular evolution of the UCC. The diamictites all have elevated chemical index of alteration (CIA) and other characteristics of weathered regolith (e.g., strong depletion in soluble elements such as Sr), which they inherited from their upper crustal source region3. δ56Fe in the diamictite composites range from -0.59 to +0.23‰, however, most diamictites cluster with an average δ56Fe of 0.11± 0.20 (2s), overlapping juvenile continental material such as island arc basalts (IABs), which show a narrow range in δ56Fe from -0.04 to +0.14 ‰4. There is no obvious correlation between δ56Fe of the glacial diamictites and the CIA, except that the diamictite with the lowest δ56Fe at -0.59 ‰ also has the highest CIA = 89 (the Paleoproterozoic Makganyene Fm.). The data suggest that the Fe isotope compositions in the upper continental crust did not vary throughout Earth history. Interestingly, chemical weathering and sedimentary transport likely play only a minor role in producing Fe isotope variations in the upper continental crust. Anoxic weathering pre-GOE (Great Oxidation Event) does not seem to generate different Fe isotopic signatures from the post-GOE oxidative weathering environment in the upper continental crust. Therefore, large Fe isotopic fractionations observed in various marine sedimentary records are likely due to other processes occurring

  4. Tracing the secular evolution of the UCC using the iron isotope composition of ancient glacial diamictites

    NASA Astrophysics Data System (ADS)

    Liu, X. M.; Gaschnig, R. M.; Rudnick, R. L.; Hazen, R. M.; Shahar, A.

    2014-12-01

    Iron is the fourth most abundant element in the continental crust and influences global climate and biogeochemical cycles in the ocean1. Continental inputs, including river waters, sediments and atmospheric dust are dominant sources (>95%) of iron into the ocean2. Therefore, understanding how continental inputs may have changed through time is important in understanding the secular evolution of the marine Fe cycle. We analysed the Fe isotopic composition of twenty-four glacial diamictite composites, upper continental crust (UCC) proxies, with ages ranging from the Mesoarchean to the Paleozoic eras to characterize the secular evolution of the UCC. The diamictites all have elevated chemical index of alteration (CIA) and other characteristics of weathered regolith (e.g., strong depletion in soluble elements such as Sr), which they inherited from their upper crustal source region3. δ56Fe in the diamictite composites range from -0.59 to +0.23‰, however, most diamictites cluster with an average δ56Fe of 0.11± 0.20 (2s), overlapping juvenile continental material such as island arc basalts (IABs), which show a narrow range in δ56Fe from -0.04 to +0.14 ‰4. There is no obvious correlation between δ56Fe of the glacial diamictites and the CIA, except that the diamictite with the lowest δ56Fe at -0.59 ‰ also has the highest CIA = 89 (the Paleoproterozoic Makganyene Fm.). The data suggest that the Fe isotope compositions in the upper continental crust did not vary throughout Earth history. Interestingly, chemical weathering and sedimentary transport likely play only a minor role in producing Fe isotope variations in the upper continental crust. Anoxic weathering pre-GOE (Great Oxidation Event) does not seem to generate different Fe isotopic signatures from the post-GOE oxidative weathering environment in the upper continental crust. Therefore, large Fe isotopic fractionations observed in various marine sedimentary records are likely due to other processes occurring

  5. Mineral composition control on inter-mineral iron isotopic fractionation in granitoids

    NASA Astrophysics Data System (ADS)

    Wu, Hongjie; He, Yongsheng; Bao, Leier; Zhu, Chuanwei; Li, Shuguang

    2017-02-01

    This study reports elemental and iron isotopic compositions of feldspar and its coexisting minerals from four Dabie I-type granitoids to evaluate the factors that control inter-mineral Fe isotopic fractionation in granitoids. The order of heavy iron isotope enrichment is feldspar > pyrite > magnetite > biotite ≈ hornblende. Feldspar has heavier iron isotopic compositions than its co-existing magnetite (Δ56Feplagioclase-magnetite = +0.376‰ to +1.084‰, Δ56Fealkali-feldspar-magnetite = +0.516‰ to +0.846‰), which can be attributed to its high Fe3+/Fetot ratio and low coordination number (tetrahedrally-coordinated) of Fe3+. Δ56Femagnetite-biotite of coexisting magnetite and biotite ranges from 0.090‰ to 0.246‰. Based on homogeneous major and iron isotopic compositions of mineral replicates, the inter-mineral fractionation in this study should reflect equilibrium fractionation. The large variations of inter-mineral fractionation among feldspar, magnetite and biotite cannot be simply explained by temperature variation, but strongly depend on mineral compositions. The Δ56Feplagioclase-magnetite and Δ56Fealkali-feldspar-magnetite are positively correlated with albite mode in plagioclase and orthoclase mode in alkali-feldspar, respectively. This could be explained by different Fe-O bond strength in feldspar due to different Fe3+/∑Fe or different crystal parameters. The Δ56Femagnetite-biotite increases with decreasing Fe3+/∑Febiotite and increasing mole (Na + K)/Mgbiotite, indicating a decrease of β factor in low Fe3+/∑Fe and high (Na + K)/Mg biotite. High-silica leucosomes from Dabie migmatites with a feldspar accumulation petrogenesis have higher δ56Fe values (δ56Fe = 0.42-0.567‰) than leucosome that represents pristine partial melt (δ56Fe = 0.117 ± 0.016‰), indicating that accumulation of feldspar could account for high δ56Fe values of these rocks. High δ56Fe values are also predicted for other igneous rocks that are mainly composed of

  6. Hydrogen isotopic composition of the Martian mantle inferred from the newest Martian meteorite fall, Tissint

    NASA Astrophysics Data System (ADS)

    Mane, P.; Hervig, R.; Wadhwa, M.; Garvie, L. A. J.; Balta, J. B.; McSween, H. Y.

    2016-11-01

    The hydrogen isotopic composition of planetary reservoirs can provide key constraints on the origin and history of water on planets. The sources of water and the hydrological evolution of Mars may be inferred from the hydrogen isotopic compositions of mineral phases in Martian meteorites, which are currently the only samples of Mars available for Earth-based laboratory investigations. Previous studies have shown that δD values in minerals in the Martian meteorites span a large range of -250 to +6000‰. The highest hydrogen isotope ratios likely represent a Martian atmospheric component: either interaction with a reservoir in equilibrium with the Martian atmosphere (such as crustal water), or direct incorporation of the Martian atmosphere due to shock processes. The lowest δD values may represent those of the Martian mantle, but it has also been suggested that these values may represent terrestrial contamination in Martian meteorites. Here we report the hydrogen isotopic compositions and water contents of a variety of phases (merrillites, maskelynites, olivines, and an olivine-hosted melt inclusion) in Tissint, the latest Martian meteorite fall that was minimally exposed to the terrestrial environment. We compared traditional sample preparation techniques with anhydrous sample preparation methods, to evaluate their effects on hydrogen isotopes, and find that for severely shocked meteorites like Tissint, the traditional sample preparation techniques increase water content and alter the D/H ratios toward more terrestrial-like values. In the anhydrously prepared Tissint sample, we see a large range of δD values, most likely resulting from a combination of processes including magmatic degassing, secondary alteration by crustal fluids, shock-related fractionation, and implantation of Martian atmosphere. Based on these data, our best estimate of the δD value for the Martian depleted mantle is -116 ± 94‰, which is the lowest value measured in a phase in the

  7. Coexistence of galenas with different Pb isotopic composition in Los Pedroches batholith area (Spain)

    NASA Astrophysics Data System (ADS)

    García de Madinabeitia, S.; Santos Zalduegui, J. F.; Larrea, F. J.; Carracedo, M.; Gil Ibarguchi, J. I.

    2003-04-01

    The Los Pedroches batholith region (S Spain) includes three separated mining districts: Linares, La Carolina and Los Pedroches. The Pb isotopic composition of thirty-three galenas from this sector has been measured. On the basis of the Pb data two types of mineralization are established. A first type including: (i) the Linares and La Carolina districts where ore-bearing filons cut Hercynian granites or their hostrocks (SE of the batholith), and (ii) the so-called "peribatholithic" ore bodies represented by scarce mines in the host-rock of the batholith; all of them exhibit homogeneous Pb isotopic compositions of: 206Pb/204Pb = 18.236, 207Pb/204Pb = 15.615, 208Pb/204Pb = 38.347 and a model age of ca. 324 Ma. The second type is represented by a huge N120^oE hydrotermal vein (the El Zumajo vein) intrusive in granitoid bodies of the batholith; the Pb isotopic composition of the vein is: 206Pb/204Pb = 18.457, 207Pb/204Pb = 15.636, 208Pb/204Pb = 38.611 and a model age of ca. 201 Ma. Analysed K-feldspars from batholithic granodiorite and granites have Pb isotopic compositions similar to those reported previously from Hercynian granites of the area (1) and to the galenas of Linares, La Carolina and "peribatholithic" ores. The whole dataset reveals a Pb evolution curve with μ_2 = 9.8 and ω_2 = 38.3, close to the model curve for the "orogen" (2). This suggests for Linares, La Carolina and the "peribatholithic" mineralizations a Pb source related to that of the granites. The pre-Tremadoc metasedimentary rocks of the area, with Pb isotopic composition (3) very close to that of feldspars and galenas studied is proposed as a possible source of Pb for both the granites and associated mineralizations, although the Pb isotopic composition of El Zumajo calls for a different origin. The observed difference in Pb isotopic ratios of the studied galenas points to, at least, two ore-forming events: (i) one relating older mineralizations and granitoid intrusives, in agreement with

  8. Mass-independent isotopic compositions in terrestrial and extraterrestrial solids and their applications.

    PubMed

    Thiemens, M H; Savarino, J; Farquhar, J; Bao, H

    2001-08-01

    In 1983, Thiemens and Heidenreich reported the first chemically produced mass-independent isotope effect. This work has been shown to have a wide range of applications, including atmospheric chemistry, solar system evolution, and chemical physics. This work has recently been reviewed (Weston, R. E. Chem. Rev. 1999, 99, 2115-2136; Thiemens, M. H. Science 1999, 283, 341-345). In this Account, observations of mass-independent isotopic compositions in terrestrial and Martian solids are reviewed. A wide range of applications, including formation and transport of aerosols in the present atmosphere, chemistry of ancient atmospheres and oceans, history and coupling of the atmosphere-surface in the Antarctic dry valleys, origin and evolution of oxygen in the Earth's earliest environment, and the chemistry of the atmosphere and surface of Mars, are discussed.

  9. Production, Isotopic Composition, and Atmospheric Fate of Biologically Produced Nitrous Oxide

    NASA Astrophysics Data System (ADS)

    Stein, Lisa Y.

    The anthropogenic production of greenhouse gases and their consequent effects on global climate have garnered international attention for years. A remaining challenge facing scientists is to unambiguously quantify both sources and sinks of targeted gases. Microbiological metabolism accounts for the largest source of nitrous oxide (N2O), mostly due to global conversion of land for agriculture and massive usage of nitrogen-based fertilizers. A most powerful method for characterizing the sources of N2O lies in its multi-isotope signature. This review summarizes mechanisms that lead to biological N2O production and how discriminate placement of 15N into molecules of N2O occurs. Through direct measurements and atmospheric modeling, we can now place a constraint on the isotopic composition of biological sources of N2O and trace its fate in the atmosphere. This powerful interdisciplinary combination of biology and atmospheric chemistry is rapidly advancing the closure of the global N2O budget.

  10. Asian anthropogenic lead contamination in the North Pacific Ocean as evidenced by stable lead isotopic compositions

    NASA Astrophysics Data System (ADS)

    Zurbrick, Cheryl M.

    This dissertation work determined the changing scope of lead (Pb) contamination in the North Pacific Ocean since the phase-out of leaded gasoline in most of the world. Chapters 1 and 2 consisted of validating our method for determining Pb concentrations and isotopic compositions in seawater. Chapter 3 established a baseline of Pb isotopic compositions (PbICs) in the western and central North Pacific in 2002. This was an ideal time to establish such a baseline because China had recently (mid-2000) ceased their use of leaded gasoline and simultaneously began consuming increasingly large amounts of coal, known to have relatively high Pb concentrations. We found subsurface waters were contaminated with Asian industrial Pb, predominantly Chinese coal emissions. In contrast, the abyssal waters were a mix of Asian industrial Pb and background (i.e., natural) Pb. Chapter 4 revisited the western and central North Pacific in 2009 -- 2011 to determine what, if any, changes had occurred in this short time period. We found that Pb in subsurface and abyssal waters of the western North Pacific were similar to Chinese aerosols. Such a large change in the PbICs of abyssal water in 9 years was unanticipated and attributed to the relatively large flux of particle-bound Pb from the euphotic zone to the deep ocean, which was in isotopic equilibrium with the reservoir of dissolved Pb. In contrast, the central North Pacific abyssal water PbICs were similar to values previously reported because of the relatively lower particulate export. Based on comparisons to baseline PbIC data, we determined that abyssal waters in the western and central North Pacific would be isotopically indistinguishable from surface waters in the next three decades. Sources of Pb to coastal California waters were reevaluated in Chapter 5. Prior studies had found that surface waters of the California Current System (CCS) were isotopically consistent with both Asian industrial Pb and US leaded gasoline, still in use

  11. Xe isotopic fractionation in a cathodeless glow discharge. [for carbonaceous meteoritic composition studies

    NASA Technical Reports Server (NTRS)

    Bernatowicz, T. J.; Fahey, A. J.

    1986-01-01

    Results are reported on the isotopic composition of Xe processed in cathodeless glow discharges in rarefied air at pressures of 20-40 microns Hg, in the presence of activated charcoal and in empty pyrex containers. Residual gas phase Xe and trapped Xe were found to be fractionated, with the trapped Xe fractionated up to 1 percent per amu. A model is presented for the fractionating process in which Xe ions are simultaneously implanted and sputtered from substrate material, with a mass dependence favoring retention of the heavy isotopes in the substrate. Results of the investigation show that plasma synthesis of carbonaceous material is unnecessary for producing Xe fractionations, and that the fractionations observed in previous synthesis experiments are probably due to implantation of ions into the synthesized material.

  12. Pore fluid constraints on the temperature and oxygen isotopic composition of the glacial ocean

    SciTech Connect

    Schrag, D.P.; Hampt, G.; Murray, D.W.

    1996-06-28

    Pore fluids from the upper 60 meters of sediment 3000 meters below the surface of the tropical Atlantic indicate that the oxygen isotopic composition ({delta}{sup 18}O) of seawater at this site during the last glacial maximum was 0.8 {plus_minus} 0.1 per mil higher than it is today. Combined with the {delta}{sup 18}O change in benthic foraminifera from this region, the elevated ratio indicates that the temperature of deep water in the tropical Atlantic Ocean was 4{degree}C colder during the last glacial maximum. Extrapolation from this site to a global average suggests that the ice volume contribution to the change in {delta}{sup 18}O of foraminifera is 1.0 per mil, which partially reconciles the foraminiferal oxygen isotope record of tropical sea surface temperatures with estimates from Barbados corals and terrestrial climate proxies. 25 refs., 3 figs.

  13. The isotopic composition of galactic cosmic ray lithium, beryllium and boron

    NASA Technical Reports Server (NTRS)

    Garcia-Munoz, M.; Mason, G. M.; Simpson, J. A.

    1978-01-01

    The isotopic composition of galactic-cosmic-ray Li, Be, and B has been measured near 100 MeV/nucleon by using the University of Chicago IMP 7 and IMP 8 cosmic-ray telescopes during 1973-1975. The measured abundances allow detailed checks of models of interstellar propagation and solar modulation to be made and conclusions to be drawn concerning the spectral forms at the source and the minimum solar modulation level. For example, comparing these results with local interstellar spectra calculated by using a 'leaky box' model, it is found that if solar modulation is ignored, there is no unique leakage mean free path consistent with all the observations. However, by taking account of a sizable level of residual solar modulation, excellent agreement is obtained between the calculated and measured abundances. Thus, these isotopic abundances confirm the old hypothesis that cosmic-ray Li, Be, and B are produced as secondaries in interstellar space.

  14. Isotopic composition of argon included in an Arkansas diamond and its significance

    SciTech Connect

    Melton, C.E.; Giardini, A.A.

    1980-06-01

    The isotopic composition of argon entrapped in a 6.3 carat, Type I, Arkansas, U. S. A. diamond (emplacement data 106 +- 3 m.y. ago) has been determined by mass spectrometric techniques. This was done by crushing the stone in a diamond crusher attached to the high vacuum inlet system of a high-sensitivity research mass spectrometer. The results show an /sup 40/Ar//sup 36/Ar value of 189 compared to a ratio of 294 for atmospheric argon, and an /sup 38/Ar//sup 36/Ar value of 0.18 almost identical to that for atmospheric argon (0.19). The isotopic data have been applied to a model of the outer Earth to test the crystallization age of the diamond. The results may be interpreted in terms of diamond crystallization about 3.1 billion years ago.

  15. Carbon-isotopic composition of soil-respired carbon dioxide in static closed chambers at equilibrium.

    PubMed

    Mora, Germán; Raich, James W

    2007-01-01

    The carbon-isotopic composition (delta13C) of soil-respired CO2 has been employed to evaluate soil carbon-cycling processes and the contribution of soil CO2 emissions to canopy and tropospheric air. These evaluations can be successful only when accurate isotope values of soil-respired CO2 are available. Here, we tested the robustness of delta13C values of soil-respired CO2 obtained after long incubations in static closed chambers that were initially flushed with soil air. The rationale of this approach is that the equilibrium carbon-isotope values of chamber-headspace CO2 are theoretically equal to those of CO2 produced within the soil. Static closed chambers were installed in replicated grass monocultures, and measurements of headspace CO2 concentrations and delta13C values were performed at regular time intervals for 24 h in July 2005. The results revealed no significant effects of grass species on headspace CO2 concentrations or delta13C values (repeated measures analysis of variance (ANOVA), P>0.1). As predicted by theory, isotope values asymptotically approached equilibrium conditions, which in our experimental setting occurred after 10 h. This good match between model predictions and our results suggests that an accurate determination of delta13C values of CO2 produced within soils is obtained through the isotopic measurement of chamber-headspace CO2 once equilibrium conditions have been reached with the underlying soils. An additional advantage of this approach is that only one sample per chamber is required, which, combined with the low uncertainties of these measurements, facilitates the investigation of the spatial (landscape) variability of soil-respired CO2.

  16. Mercury Stable Isotopic Composition of Monomethylmercury in Estuarine Sediments and Pure Cultures of Mercury Methylating Bacteria

    NASA Astrophysics Data System (ADS)

    Janssen, S.; Johnson, M. W.; Barkay, T.; Blum, J. D.; Reinfelder, J. R.

    2014-12-01

    Tracking monomethylmercury (MeHg) from its source in soils and sediments through various environmental compartments and transformations is critical to understanding its accumulation in aquatic and terrestrial food webs. Advances in the field of mercury (Hg) stable isotopes have allowed for the tracking of discrete Hg sources and the examination of photochemical and bacterial transformations. Despite analytical advances, measuring the Hg stable isotopic signature of MeHg in environmental samples or laboratory experiments remains challenging due to difficulties in the quantitative separation of MeHg from complex matrices with high concentrations of inorganic Hg. To address these challenges, we have developed a MeHg isolation method for sediments and bacterial cultures which involves separation by gas chromatography. The MeHg eluting from the GC is passed through a pyrolysis column and purged onto a gold amalgam trap which is then desorbed into a final oxidizing solution. A MeHg reference standard carried through our separation process retained its isotopic composition within 0.02 ‰ for δ202Hg, and for native estuarine sediments, MeHg recoveries were 80% to 100%. For sediment samples from the Hackensack and Passaic Rivers (New Jersey, USA), δ202Hg values for MeHg varied from -1.2 to +0.58 ‰ (relative to SRM 3133) and for individual samples were significantly different from that of total Hg (-0.38 ± 0.06 ‰). No mass independent fractionation was observed in MeHg or total Hg from these sediments. Pure cultures of Geobacter sulfurreducens, grown under fermentative conditions showed preferential enrichment of lighter isotopes (lower δ202Hg) during Hg methylation. The Hg stable isotope signatures of MeHg in sediments and laboratory methylation experiments will be discussed in the context of the formation and degradation of MeHg in the environment and the bioaccumulation of MeHg in estuarine food webs.

  17. Isotopic composition of dissolved iron in the Equatorial Pacific and the Southern oceans

    NASA Astrophysics Data System (ADS)

    Radic, A.; Lacan, F.; Jeandel, C.; Poitrasson, F.; Sarthou, G.

    2009-12-01

    Iron is a fundamental element linking ocean biogeochemistry and climate. Iron isotopes are a very promising tool for the study of the iron oceanic cycle, notably for tracing its sources to the ocean and/or for studying its speciation. Several studies reports iron isotopic data in the marine environment: in plankton tows, pore waters, aerosols, seafloor or marginal seas (Bergquist and Boyle, 2006; Severmann et al., 2006; De Jong et al., 2007). To link these isotopic data together and to fully study the iron isotope marine cycle, we need to document the central reservoir in the marine environment : dissolved iron in seawater, espacially in High Nutrient Low Chlorophyll (NHLC) areas. So far there are very few comunicated data of dissolved iron isotopic composition in the open ocean (Rouxel, 2008; Lacan et al., 2008; John and Andkins, 2009;). Here, the first profiles in HNLC areas will be presented : 2 full-depth profiles in the Equatorial Pacific Ocean (EUCFe 2006), 2 full-depth profiles in the Atlantic sector of the Southern Ocean (Bonus-GoodHope 2008) and some data from the Kerguelen area (Southern Ocean, KEOPS 2005). δ56Fe values range from -0.7‰ to more than 1.0‰. All the samples from the Equatorial Pacific Ocean display positive values (heavy iron) whereas samples from the Sourthern Ocean display rather negative values (light iron), especially around 450 m deepth. These results will be discussed in terms of iron sources to ocean. Potential applications of this new tracer for studying internal oceanic processes, such as biological uptake, will be discussed.

  18. Isotopic and elemental compositions of stardust and protosolar dust grains in primitive meteorites

    NASA Astrophysics Data System (ADS)

    Bose, Maitrayee

    This dissertation presents the results and implications of the isotopic and elemental analyses of presolar silicate grains from the primitive chondrites, Acfer 094, SAH 97096, and ALHA77307. Oxygen-anomalous, C-anomalous, and N-anomalous grains were identified by O, C, and N isotopic imaging, respectively, using the NanoSIMS 50. Subsequently, the elemental compositions of the grains carrying the anomalous isotopic signatures were acquired in the PHI 700 Auger Nanoprobe. Some silicate grains with unique O isotopic compositions were measured for Si and Fe isotopes. The isotopic analyses indicate that a majority of the silicate and oxide grains are 17 O-rich with solar to sub-solar 18 O/ 16 O ratios and come from less than 2.2 M⊙ Red Giant or Asymptotic Giant Branch stars. The second most abundant fraction of grains show large 18 O excesses and come from core collapse supernovae. The next most abundant fraction of grains comes from high metallicity AGB stars of approximately solar mass. A minor fraction of the grains exhibit large excesses in 16 O and formed in core collapse supernova ejecta. Grains with extreme 17 O excesses are the latest addition to the presolar grain inventory. These grains may come from binary star systems where one star goes nova. Numerous presolar SiC and N-anomalous carbonaceous grains were identified in the matrix of ALHA77307. The SiC grains are predominantly mainstream grains and may have condensed in 1-3 M⊙ AGB stars. The carbonaceous grains may have formed by ionmolecule reactions in the protosolar nebula or interstellar medium. A few carbonaceous grains exhibit 13C-rich compositions; grains with such compositions are rare, which implies that either the fractionation effects that produce C anomalies in opposite directions cancel them out or secondary processing destroyed grains with C anomalies. The elemental compositions of the silicate grains are predominantly nonstoichiometric (61%), with some grains exhibiting olivine- or pyroxene

  19. The tungsten isotopic composition of the Earth's mantle before the terminal bombardment.

    PubMed

    Willbold, Matthias; Elliott, Tim; Moorbath, Stephen

    2011-09-07

    Many precious, 'iron-loving' metals, such as gold, are surprisingly abundant in the accessible parts of the Earth, given the efficiency with which core formation should have removed them to the planet's deep interior. One explanation of their over-abundance is a 'late veneer'--a flux of meteorites added to the Earth after core formation as a 'terminal' bombardment that culminated in the cratering of the Moon. Some 3.8 billion-year-old rocks from Isua, Greenland, are derived from sources that retain an isotopic memory of events pre-dating this cataclysmic meteorite shower. These Isua samples thus provide a window on the composition of the Earth before such a late veneer and allow a direct test of its importance in modifying the composition of the planet. Using high-precision (less than 6 parts per million, 2 standard deviations) tungsten isotope analyses of these rocks, here we show that they have a isotopic tungsten ratio (182)W/(184)W that is significantly higher (about 13 parts per million) than modern terrestrial samples. This finding is in good agreement with the expected influence of a late veneer. We also show that alternative interpretations, such as partial remixing of a deep-mantle reservoir formed in the Hadean eon (more than four billion years ago) or core-mantle interaction, do not explain the W isotope data well. The decrease in mantle (182)W/(184)W occurs during the Archean eon (about four to three billion years ago), potentially on the same timescale as a notable decrease in (142)Nd/(144)Nd (refs 3 and 6). We speculate that both observations can be explained if late meteorite bombardment triggered the onset of the current style of mantle convection.

  20. Mixing ratio and carbon isotopic composition investigation of atmospheric CO2 in Beijing, China.

    PubMed

    Pang, Jiaping; Wen, Xuefa; Sun, Xiaomin

    2016-01-01

    The stable isotope composition of atmospheric CO2 can be used as a tracer in the study of urban carbon cycles, which are affected by anthropogenic and biogenic CO2 components. Continuous measurements of the mixing ratio and δ(13)C of atmospheric CO2 were conducted in Beijing from Nov. 15, 2012 to Mar. 8, 2014 including two heating seasons and a vegetative season. Both δ(13)C and the isotopic composition of source CO2 (δ(13)CS) were depleted in the heating seasons and enriched in the vegetative season. The diurnal variations in the CO2 mixing ratio and δ(13)C contained two peaks in the heating season, which are due to the effects of morning rush hour traffic. Seasonal and diurnal patterns of the CO2 mixing ratio and δ(13)C were affected by anthropogenic emissions and biogenic activity. Assuming that the primary CO2 sources at night (22:00-04:00) were coal and natural gas combustion during heating seasons I and II, an isotopic mass balance analysis indicated that coal combustion had average contributions of 83.83±14.11% and 86.84±12.27% and that natural gas had average contributions of 16.17±14.11% and 13.16±12.27%, respectively. The δ(13)C of background CO2 in air was the main error source in the isotopic mass balance model. Both the mixing ratio and δ(13)C of atmospheric CO2 had significant linear relationships with the air quality index (AQI) and can be used to indicate local air pollution conditions. Energy structure optimization, for example, reducing coal consumption, will improve the local air conditions in Beijing.